With a pair of legendary leading men never before seen on screen together, a December release date in the thick of awards season and a modern crimescape narrative that became an instant classic, Michael Mann’s “Heat” probably should have been up for a slew of Oscars. Somehow, that didn’t happen.

Warner Bros. was coming off an impressive Oscar streak in 1995, with films like “The Accidental Tourist,” “Dangerous Liaisons,” “Driving Miss Daisy,” “Goodfellas,” “JFK,” “Unforgiven” and “The Fugitive” doing a lot to bolster the company’s archives. This particular year brought an interesting assortment of films to play with: Clint Eastwood’s “Bridges of Madison County,” Marc Rocco’s “Murder in the First” with a dynamite performance by Kevin Bacon, etc. Yet the film which netted the most nominations for the studio was summer tentpole “Batman Forever.”

But “Heat” should have been all over the place. Nominations for best picture and best director would have been deserved. With a cast full of stars to pull from, someone probably should have ended up among the Academy’s 20 acting nominees (perhaps Ashley Judd’s put-upon crime wife, if choosing between Robert De Niro and Al Pacino is too much to ask).

Below the line, Dante Spinotti’s cinematography boats so many iconic frames and is so wonderfully representative of Mann’s typically robust mise-en-scene. The editing — with four cutters credited — whips the massive 170-minute opus together with a steady pace and lots of peculiar but interesting breakaways to liven the world within the picture. By itself, the bank heist which draws the second act to a close should have put sound nominations on the table.

It’s a beast of a movie. But it just wasn’t taken seriously as a prestige picture. It did well enough at the box office ($67 million in domestic receipts), but maybe it was burdened in the industry with being “genre.” That having been said, it was certainly respected for pulling away from the superficial and into thematically innervated waters. Here’s the nut graph from Todd McCarthy’s Dec. 5 review:

“Heat” occupies an exalted position among the countless contemporary crime films. Stunningly made and incisively acted by a large and terrific cast, Michael Mann’s ambitious study of the relativity of good and evil stands apart from other films of its type by virtue of its extraordinarily rich characterizations and its thoughtful, deeply melancholy take on modern life.

So what happened? I don’t know — I was in high school. But the question was already in the air that season. A Jan. 16, 1996 Variety column asserted that a “looming question” was whether the film would “get a warmer reception from Oscar voters than it did from the Golden Globe contingent,” with a particularly juicy quote from Mann calling the experience of directing De Niro and Pacino “a dive on the high board, with 3.9 difficulty.” An earlier piece noted that the Hollywood Foreign Press Association may not have been able to see the late-breaking film in time for it to register, though that kind of thing was less of a problem for Oscar voters back then, when the Academy Awards weren’t held until late March.

Whatever the case, Warner Bros. did the usual diligence, as you can see above, taking out print ads talking up the critical approval. Alas, it was to no avail.

The film’s 20th anniversary is thankfully not going unnoticed, though it does come at a time when the Regency catalog is shifting away from Warner Bros. and over to Fox, slowing things down a little bit. A screening and Q&A event has been set for the Toronto Film Festival Tuesday night with Mann in attendance. I’m also told plans are in motion for Fox to release a special DVD/Blu-ray next year. “We have a great relationship with him,” Fox Home Entertainment EVP James Finn told me. “We did the definitive edition on ‘The Last of the Mohicans’ and he loves our team and restoration guys. We’re going to honor it.”

When the time comes, it will be interesting to see what, if anything, Mann wants to change about the film. “The litmus test for me is when it goes to a new format, do I want to make changes to it,” the notoriously meticulous director told me in a chat earlier this year. Indeed, the only minute alterations he made when “Heat” went to Blu-ray for the first time was snipping a pair of lines from Pacino and Diane Venora, leading to a mere three-second difference in running time. Compare that to the more overt tinkering on films like “Mohicans,” “Ali” and “Miami Vice,” and you can tell “Heat” is pretty much the film Mann wanted to make.

It’s just a shame it wasn’t a film the Academy wanted to nominate. But it’s a good lesson about the Oscars: The immortality of a classic is not dependent upon the time capsule approval of awards voters. Mann’s “Heat” follow-up was the 1999 whistle-blower drama “The Insider.” Seven nominations, zero wins — yet it’s widely considered his best work, and easily one of the best films of that year.

Greatness simply endures. Everyone eventually catches up in the end.