No, Jigglypuff's sleep does way more than 25%, and has a high chance of knocking nearly every character off the screen. Unfortunately very few know how to use the move properly, and even fewer can use it on a regular basis. (It has ultrasmall range, and leaves you wide open if you miss.)
And anyone who says SSB:M is perfectly balanced has yet to play any of the great SSB:M players. Any of them will tell you there are levels of good players.
You will NEVER, EVER see a good player under Mr. Game and Watch defeat Marth. I'm sorry, it won't happen. If you lose, then you aren't a good player, simple as that.
Roy is actually sort of weak. He's slower, and his counter has a smaller window. Of course this is backed up by higher damage, but the slowness, in addition to a much worse spiking move and faster falling rate means that he is vastly inferior to Marth.
Pikachu lost its ranking from SSB to SSB:M. It's now a lot weaker compared to the other newer characters. Still an effective opponent however.
Jigglypuff is a highly disputed character. There is no doubt it is a highly regarded one, but whether it ranks at the Level 1 character rank has yet to be fully decided. Either way, when someone plays Jiggly and knows what he/she is doing, watch out.
Shiek is immensly popular also. (Something I am a part of :D) She is the fastest character in the game, and she can rack up combos like no other. She also has decent recovery and falling rate, making her an excellent choice, and thus ranked in the Level 1.
Marth is also immensly popular, ranked in Level 1. He is very fast, decently strong, and has crazy reach on his sword. (The tip of his sword does the most damage, unlike Roy, where the center of the blade does the most damage.) He also has a nice fall rate, and a recovery move that can get you back from nearly any situation. (Repetitively hit b -> in the direction of the map floor. Just make sure you don't continue the combo, that'll kill you. Just do the first swing over and over.) This is my best character, although I like playing as Shiek more.
Bowser is not that bad of a character, ranked at level 4. Although his size is a big problem, his attacks are crazy good, and he has a decent set of combos. His decent horizontal recovery allows him to stay alive when he does get knocked off.
Well, I think that's enough for now.