The first iPad came out five years ago today. Lately, most of what you hear about the tablet is that sales are in a slump, and it’s true: year-over-year sales have been down for four straight quarters, and, in a couple of weeks, we’ll find out whether it will be five straight.

But even a slumping iPad is still a formidable sales juggernaut—Apple sold a total of 63.4 million iPads in those four quarters, generating $27.8 billion in revenue. It’s not a patch on the iPhone, which can sell more units than that in a single quarter, but the tablet lineup is still generating a lot of money for Apple.

Today we’re taking a quick walk down memory lane, revisiting our reviews of each iPad and remembering what each model is best remembered for.

The iPad: It begins

The first iPad is, believe it or not, the only version that isn’t still getting software updates. It was never upgraded to iOS 6, even though its immediate successor is still kicking (more or less) with iOS 8. It launched with a then-new Apple A4 chip, 256MB of RAM, and a special version of iOS 3.2 that the iPhone didn’t get—the iPhone and iPad weren’t running the same version of iOS until iOS 4.2 came out in November of 2010.

From our review:

Truthfully, this device is one that can only really be understood by playing with it firsthand (we know, it took us more than 18,000 words to tell you that). No matter how many words get spilled on the iPad, there's still no simple way to describe how it feels and how it's different from a typical computing or smartphone experience. Those of us on staff who were highly skeptical about the iPad before having touched it had a very different understanding of it after spending some serious time with the device. This is likely to be the case with most users. The best way for us to sum up our collective and unanimous conclusion on the iPad, is to say that it's the first device to substantially deliver on the promise made by the iPhone and, in some respects, the Newton. Both of these earlier Apple products gave us glimpses at what a real, usable, purpose-built tablet computer might one day look like, and the iPad at long last gives us the complete picture. So in a sense, the iPad is both the end of a long journey and the start of a new one. We can't wait to see where it takes us next.

The iPad 2: Let’s go faster

Apple, as a company, is pretty good at second-generation products. Designs like the iPad 2 and the 2010 MacBook Air exemplify its ability to identify key problems with first-generation designs and fix them. The iPad 2 was so solid that Apple sold it for three years after it launched in 2011. The Apple A5 provided a big boost to CPU and GPU performance, jumped to 512MB of RAM, and reduced the tablet’s size and weight. And while it has nothing to do with the hardware itself, it’s worth remembering that the iPad 2 was one of the last products introduced by Steve Jobs before his death in October 2011.

From our review:

When Steve Jobs introduced the iPad 2, he insisted that the rumors were wrong, that this device was no tweak or speed bump—it was a major update to Apple's original tablet. He may have been right in some respects, but overall, we have to disagree. The iPad 2 is an iteration on the original iPad in order to optimize the user experience, both inside and outside. Despite our complaints, the results are mostly good. The iPad is now particularly attractive to new buyers—moreso than the original was. Apple has a better idea now of what the market wants and has made a move on what it thinks are the most important elements: size/weight, cameras (even if they aren't the best), and overall performance. The current device feels more refined than the original in almost every way, and it strives to offer a premium tablet experience via iOS. If you own an original iPad, we'll be honest with you: there's not much reason to run out and upgrade unless you have specific needs when it comes to the iPad 2's cameras or CPU/graphics performance. The performance gains are indeed noticeable, though, so we wouldn't blame you if you wanted to upgrade just to ensure that your hardcore games don't hiccup like they used to. Still, as we recently wrote in our review of the Motorola Xoom, there are few reasons to buy something else over an iPad 2 as things stand today—the alternate offerings are incomplete and Honeycomb still needs work, though both of those elements may change later in the year. For now, though, the iPad 2 is the best tablet currently available, despite our various nitpicks.

The third-generation iPad: The iPad goes Retina

Apple dropped its iPad numbering scheme for a while with the introduction of this tablet in early 2012—it and its immediate successor were just called “the new iPad” when they launched.

This iPad was the first to use a Retina display, and though the panels have improved since then, all of the full-size iPads to date have used the same screen size and resolution. But that display came with some compromises—this iPad was a bit larger and heavier than the iPad 2, and its huge battery took a long time to charge. Its A5X chip, which kept the same dual-core CPU as the A5 but amped up the GPU and bumped the RAM to 1GB, isn’t always up to the task of driving that display.

From our review:

The third-generation iPad may not save your soul, but it does make a few solid improvements over the already successful iPad 2: "retina" display, support for LTE cell networks, voice dictation, and a much improved rear-facing camera. Considering that it's the same price as the iPad 2 was at its launch (starting at $499 for 16GB WiFi-only iPad 3s), it's a fine product. But those looking for significant performance improvements over the iPad 2 will be disappointed, as might those who have no need for a high-resolution display. The iPad 3's updated processor and memory bump left it performing at about the same level as the iPad 2, so it's clear that most technical improvements exist to keep the retina display chugging. When I purchased the iPad 3 for this review, I wasn't sure if I'd keep it once the review was done. But after having used it for several days, I particularly like my LTE data options (and the Verizon iPad's ability to share LTE over a wireless hotspot), which is the main factor convincing me to keep it. The nicer-looking display is a bonus, but if not for the LTE and hotspot features, I would seriously consider sticking with my iPad 2 for another year.

The fourth-generation iPad: Lightning strikes

The fourth-gen iPad was introduced a short seven months after the third-generation model, and, while it looked the same from the outside, its internals made big strides forward. The A5X was exchanged for an A6X that doubled CPU and GPU performance, and dual-band 802.11n Wi-Fi and Bluetooth 4.0 mean that this iPad is compatible with new iOS 7 and iOS 8 features like Handoff and AirDrop.

This was also the first iPad to drop the old 30-pin connector in favor of the Lightning port, which was its only physical change.

From our review:

In many ways, the iPad 4 is a subtle refinement of the previous iPad 3. The processor is at least twice as fast, as Apple claims, though in real-world use you may not notice that much. If you tend to run more demanding apps, particularly for graphics, video, or audio creation, the extra oomph pays off. Gaming doesn't seem to benefit too much from the improvements just yet, but we don't doubt game developers are upgrading their respective bags of OpenGL ES tricks to find new ways to push the hardware. If you own an older iPad and skipped the iPad 3 because performance wasn't any better, now may be as good a time as any to pull the trigger. Not only should you experience improved performance, you will also see the benefits of a Retina display. If you own an older iPad and skipped on the iPad 3 because of the increased weight, you might consider an iPad mini or just wait and see what Apple has next year. If you were waiting to see how the iPad would stack up against the latest Android and Windows tablets, it's clear that the iPad can easily hold its own with respect to performance and battery life. The Nexus 10 is so far the only device that appears as though it can compete when it comes to display quality, and it certainly is a bit cheaper. But, no surprise, Apple doesn't play the race to the bottom game when it comes to pricing, and the company seems to be happy with its performance in that respect. Even at $499 to start, the iPad is still a great value overall.

Listing image by Jacqui Cheng