Um....Greninja isn't light at all, he's a middleweight character whose weight is very close to Sonic and Pac-Man's and we're about the 30-32th heaviest. And while its true that we are are a fast faller, a fall speed chart I read says that you are too, and you're not the only one with combos here:
- Nair > Almost Anything (Dtilt+,Jab, Utilt+, Fsmash, Usmash)
- Nair > Footstool > Dair > Nair > Another footstool or Usmash
- Dtilt > Dash Attack+, Fsmash, Dash Grab, Usmash, SideB (not really a combo, but if I read an air dodge you're dead)
- Dthrow > Fair, a guaranteed kill setup I might add at higher %
- Uthrow > Uair, SideB (again, an airdodge bait, but a lethal one)
- Falling Uair > Dsmash/Fsmash, or a Dair
- Utilt > Usmash, Bair, Uair (another guaranteed kill setup)
Looks like you didn't know just how strong our own combos can be, while you may be able to combo us the same is true in reverse.
___
And about Eruption killing Mega Man, don't you need to charge up Eruption for it to hit under the ledge or even have enough power to kill us? Can't you be hit out of the charge? If that's the case, couldn't I just shoot lemons, metal blades, or even a crash bomb to get around that? And while Mega Man's kill options aren't the best, we do have kill setups in Fullhop Diagonal Metal Blade > Mega Upper (even if you shield it we still get a grab) and DICIT leads into many of his kill options as well, and I personally feel Mega Man might climb a few spots up on the tiers as more Mega Men master it (its very tough to pull off tho). This is just theorycraft, but I hear Ike's recovery is fairly limited himself, and I hypothesize that it might be possible to screw with your recoveries using Metal Blades, Dair, Bair, or even lemons.
Again, I still don't have a whole lot of experience with Ike so I don't mean to outright disagree with the matchup (although I can't really imagine Ike being a threat to Mega Man, at least not compared to our 4 actual bad MUs), but I feel that some things stated are incorrect or questionable.