I really would disregard any super-early tier lists. Just look at how flawed Brawl's first tier list was.
- Dedede, G&W and R.O.B are extremely powerful(C+, C, C- now)
- Donkey Kong is better than Diddy(Diddy is A+ while Donkey is now D)
- Kirby and Lucario are high-tier(Lucario is C+, Kirby is D)
- Olimar and ZSS are mid-tier(Olimar is A+ now, ZSS is B)
- Bowser is mid-tier(F)
- Sonic is horrible(D, not as bad as E or F)
- Zelda is better than Sheik(Zelda is second worst character at F, Sheik is D)
- C. Falcon is worse than Ganon(Ganon is now the worst)
- Peach is worse than Luigi(Peach is C-, Luigi is E.)
Mega Man has way too many tools to realistically be a horrible character. He's probably in Brawl Olimar's situation where no one really knows how to play him and regard him as crap because of it.