I really don't like "All Star" rosters. I much prefer if there is at least an underlying premise that makes some kind of sense.

Of course. This isn't a contest... nothing comes close to it, look at how many iconic characters!

Definitely way up there for sure.

Yeah.

I guess the gameplay is poor though...at least from what I hear.

OT: It's definitely up there for me, both in terms of diversity and how iconic the roster is. 

The cool part is that a huge percentage of the characters are all original IP (or owned by subsidiaries).

In my opinion, Nintendo takes home the trophy for largest in-house character lineup (Correct me if this is inaccurate. The fanboy in me talks a lot.)

Honestly, I think Project M had the best roster. Each character had something that made them special. You can pick out any character in PM, like Mario, Jigglypuff, or Samus, and I can think of stuff that separates them from everyone and what's really unique about them for a looong time.

However in Smash 4, while the roster is impressive, some of the characters...just don't seem as impressive compared to other characters. Swordsman are often look down upon, and some characters have simply less unique things over other characters. If you were to tell me what makes characters like Lucina, Jigglypuff, Palutena, and Samus unique...I honestly can't go on very long.

Let's take Samus for example. What makes Samus so unique compared to the rest of the cast in PM is that she has the ability to perform a Super Wavedash, can crawl in her morph ball form and actually attack from it, has an ice mode where half of her move changes and can be used strategically, and can cancel her missiles lag on landing and can effectively send a barrage of missiles when using platforms. Just only a sample of what I can give.

Whereas Samus in Smash 4 (which I play a lot btw)...honestly all I can think as unique is that her zair is a good approach option compared to other tether characters (which is also applicable in PM, just missiles are better) and...a sandbag character. :/

That's an interesting observation. In my opinion, PM made all of the characters level with each other; it basically destroyed the melee tier list for me.

It had the best roster since the N64 game.

I will say Killer Instinct comes a good 2nd place due to its variety of different characters and play styles. Its one of only fighting games I know of that doesn't have any character clones or spin-offs ie Ryu/Ken, Subzero/Scorpion.

Yeah, gotta say J-Stars can stand next to Smash in having the best roster. So nice to see a lot of Jump's best in one big game. @_@