Eh, if I had to go top 5, I'd say:
Wesker
Taskmaster
Magneto
Amaterasu
Dante
Wesker's got it all. 1.1 million HP, an incredible rushdown game, solid chip-away with jump-gun-downport pressure which is hilarious. He's also got AMERICA'S FAVORITE COMBO, and his gun OTG assist is incredibly useful for a lot of characters that have problems OTGing on their own. His only real issue is that his level 1 hypers are pretty bad in terms of usefulness- Maximum Wesker doesn't have any invincibility and its damage is pretty bad, but it crosses up like a motherfucker midscreen which is absolutely ridiculous, and his counter is "that thing you accidentally use when you intend to DHC into Maximum Wesker". However, as a 1.1m HP character with effectively no bad matchups, Wesker definitely takes top spot.
Taskmaster gives him a run for his money though, IMO. He has a MUCH better chip-away ranged pressure game with his arrows, both in normal form and in hyper form, and his mobility is great to boot. He also does plenty of damage with Mighty Swing BNBs, and has solid mid-range rushdown pressure. He's also got the staying power that 1.1 million HP affords, which is definitely a big deal when you're going up against more damaging characters. Finally, his arrow assist is very useful for covering you while you close the distance or just for helping with ranged pressure.
Magneto being third is mainly because of his HP. Disruptor gives him solid ground keepaway (but his air keepaway is kinda meh, so any character with a solid jumpin toasts him), and he's also got absolutely vicious mixups and VERY damaging combos. His Disruptor assist is also great, and he has 3 very useful Hypers in the form of Magnetic Shockwave (covers the whole screen, and can be DHCed immediately without sacrificing any power), Magnetic Tempest (which works with the DHC Glitch for lulzy power), and GRAVITY SQUEEZE (which is just straight up ridiculous). The only issue I have with him is that his 850k HP makes him fold really badly against any character that can mount effective pressure against him. If he starts a match off on the wrong foot he can really end up in trouble.
Amaterasu is a character that first got "discovered" back when Sentinel was the retardedly powerful top dog, mainly because of her tiny hitbox and solid keepaway in the form of Cold Star. She's got a ridiculously huge movepool, with tools for keepaway, melee power, midrange, and closing the distance all in one. Okami Shuffle is a great Hyper as well, and Cold Star makes a great assist (using it to cover Doom's Hidden Missiles, anyone?) However, she's merely "okay" against pressure- paper helps her and counters work if your timing is good, but 800k HP means she folds really fast against anyone that can land a hit in melee, which isn't terribly hard.
Dante's 5th because of the power of his teleport mixups, "decent" keepaway outside of Devil Trigger in the form of Missile Swarm (though it doesn't keep people out for long enough to actually make a difference), and general solid moveset. He's also got great supers for DHCing, since a DHC into or through Devil Trigger is extremely useful, and his gun super is fantastic at all ranges. However, again, 900k HP hurts him a lot since he tends to get nicked in melee.