That picture is missing the Other M base power suit and the final Fusion Suit. As for my favorites...



B2: Metroid 2 introduced the Varia Suit to the series, and I honestly think Metroid 2's fantastic art and sprite are a big part of why the Varia Suit had become such a series staple. It really makes Samus feel like a tank.



N3: I've never been a huge fan of the Gravity Suit's color scheme... But man did Samus Returns make it look good. I love the almost medieval look of the armor plating.



L3: The Light Suit is the single most satisfying suit to obtain in Metroid history, and it looks slick as hell. It's a radical departure for the series, but unlike the Fusion Suit, it still communicates the power and coolness Samus should have. I love how the lights on the chest match Luminoth wall art designs.



M1: I do not like the Other M Varia Suit. It always looks off. Yet Smash 4 redeemed the suit, and I think a large part of that is just the superior color scheme. No more piss yellow and a much more pleasant shade of green, along with a texture that feels less glossy and more like actual metal. So one of my least favorite looks was retooled into one of my favorites.



L1/J1: Metroid Prime 1's Varia Suit will always hold a special place in my heart, but Prime 2/3 blows it out of the water. I own the Figma version of this design and it's a fucking joy to look at.