A little more on Mega Man 10

Well, I beat the game in all its modes now and have played as all 3 characters.  For me personally, this is probably going to be the Mega Man game I turn to for any quick fix I need, at least for a while.  I suppose 9 would offer just about the same thing that 10 does, but 10's just got more for me.  Mostly, it's the challenges that will bring me back.  9's challenges were essentially pseudo-achievements you did through regular gameplay.  For 10, it actually has custom-designed levels to play through.  You can beat them normally, but you only get full completion when you do so without taking damage.  For Hard Mode challenges, you even have to use just the Mega Buster.  Getting the full completion is what's going to make this intriguing for me, and I don't anticipate myself getting all of them.  I'll be proud if I can just get in 90%.
Read more past the break to get a summary of the alternate characters available for the game.
+ Charge shot
+ Slide
+ Shield against projectiles
- Takes more damage.
- Only 2 shots can be on the screen at once.
Honestly, Proto Man just feels like an Easy Mode for me, and not just because I played him on Easy Mode.  The fact he takes more damage is effectively negated when you're not taking damage.

Bass
+ Built-in turbo button
+ Angled shots, can shoot straight up
+ 5 shots at a time
+ Slide
+ Free flying with Treble
- Half-power in shots
- No shooting through scenery
- Cannot run & shoot
As you can see, it's an entirely different game with Bass.  Some of the tactics you could do as Mega Man just won't work with Bass.  Of course, you compensate for that with entirely different tactics.  The Keeper mini-boss (Strike Man's goalie) just dies because you can sit right under it and shoot.  Have fun with it, because Bass has plenty of action to offer you without being easy.