A game you've probably never heard of.
Now that you've recovered from the shock, I'll continue.
I really can't describe this game to someone who's never played it. Gone are the Master Robots and the Wily antagonist. Instead, we have the Bonne family, led by the sexy Tron. (Get it? Tron Bonne?) And instead of Dr. Light teleporting Rock into fortresses, you've got Roll lower him into underground caverns.
The bosses are exactly what you'd expect from an RPG. Huge, tough to kill, with weaknesses to specific weapons.
The storyline is really mindblowing when you get to that final twist at the end, so I won't spoil it for you.
If you can find this somewhere, buy it. It's worth the 5 dollars it probably costs by now.