Jim was an ordinary earthworm, doomed to scrape along the fetid belly of the earth, until he took refuge in a Super Suit and became a super-powered worm hero. The saying goes that clothes make the man, and in the case of Jim, clothes made the worm. He became extremely powerful, able to whip, shoot, and snot his way through interplanetary adventures, saving Earth in the process.
Unfortunately, the suit had it's limits. In several levels, Jim has to climb out of his suit and traverse alone, reminding the player of how puny Jim was without his suit. Another ability the suit seems to lack is the ability to maintain a franchise. Poor Jim.
Samus is a no-brainer to be considered for best suit. Hers was one of the earliest and most iconic, and best of all it even helped to conceal one of gamings' formerly-best-kept secrets: that the man under the suit wasn't a man at all; it was a woman.
Samus has had many suits: for example, Fusion, Zero, and Bathing, but the one that tops them all is the Varia Suit. Not just because picking most other suits would make me look like a creep; I'm picking it because of how iconic the suit is. If I walked down the street in the Phazon suit, I'd probably be a pretty powerful dude, but no one walking by would be like, "Oh cool, Metroid!" They'd probably be more like "holy shit please don't kill me with your gun arm."
No one has had greater success in video game suits than Mario; you could do a whole list with his suits. But when it comes down to picking one, picking the absolute best suit, the answer is clear: the Tanooki Suit. Not only does it offer the functionality of another great suit (the Raccoon Suit) it even goes above and beyond with the added ability to turn into a statue and have enemies simply pass you by. The Tanooki Suit is also much "suit-ier" than the Raccoon Suit, offering a full body raccoon onesie instead of just ears and tail. Just in terms of amounts of fabric used, Tanooki is clearly a better value than almost any other suit Mario has worn. Except maybe the frog suit, but that's only good in underwater levels, which suck anyway.