My current signature highlights the ten characters (five Vets, five Newcomers) that I am the most interested in playing in SSB4, for various reasons. It should also be noted that I've always been a fairly casual Smasher by necessity (i.e. lack of people to play with), though I do intend to get into the SSB4 groove (the main reason I joined this forum).
Of those currently revealed:
Luigi
--He's been my main for the past three Smash games. I ended up preferring him in Smash 64, and have used him ever since. Plus he's better than Mario in every conceivable way inside and outside Smash lololololol
Lucario
--I was not familiar with Lucario pre-Brawl. He didn't serve as a fitting "replacement" for Mewtwo (I didn't know about Mewtwo's Brawl situation until much later), but I ended up coming to appreciate Lucario in his own right, so I'm glad he's returned to SSB4.
Olimar
--Olimar was someone I latched onto pretty quick. As a Pikmin fan, I had appreciated his inclusion, and his tactical Pikmin-based playstyle
Wii Fit Trainer
--Of the E3 Newcomers, WFT was the one that intrigued me the most (since I had no personal connection to Mega Man or Villager). Even after Rosalina and Little Mac, she continues to hold that title. Her graceful, agile nature and the novelty of the character and dat Wii Fit Tushy have made her the standout Newcomer thus far.
And as for the remaining to-be-confirmed Veterans and probable Newcomers:
Ganondorf
--As a huge fan of the character, I naturally ended up using him a lot in Melee, and then in Brawl. His mobility and speed were very poor in Brawl. I'm hoping that his mobility/speed is either improved, or that they give him Super Armor to counterbalance his general sluggishness.
Mewtwo
--Other than Luigi and Ganondorf, he was my most-used character in Melee. That was my least-played Smash game, alas, but Mewtwo left an immense impact. His playstyle, design, and pretty much everything else about him appealed to me greatly. His absence from Brawl, therefore, was woeful, and the fact that he's highly probable to return this time around is a prospect that excites me greatly.
King K. Rool
--Of the mainline DK platformers, I've only played DK64 (so I don't have the DKC nostalgia going for me). Even so, I'm a fan of the character, and think he's both the most deserving and most fitting candidate for a DK Newcomer. He has great moveset and playstyle potential, and his zaniness would go well with the hectic universe of Smash.
Ridley
--Much like K Rool, I've only played a small part of the Metroid franchise (namely, the Prime trilogy). Yet Ridley also appeals to me, and for similar reasons as K Rool -- a deserving and fitting Metroid Newcomer with high moveset and playstyle potential.
Takamaru
--I've only learned of the existence of Takamaru in the past six months. I haven't played the original Murasame game, but the prospect of getting a legit Edo-period samurai in Smash is too cool to pass up.
Shulk
--Shulk is in my signature because he basically seems cool, though I haven't played Xenoblade. His inclusion or exclusion is not quite as much a concern compared to the rest. You could swap Shulk out of my signature for any other interesting-to-me Newcomer (Palutena is the most probable candidate out of such a category of Newcomers).
It's conveniently turned out that the characters I want most for SSB4 also happen to be pretty likely, with Mewtwo/K Rool/Ridley/Takamaru especially having very strong cases backing up their probability of inclusion. So it's very likely that I will be very mostly satisfied with the SSB4 roster. 8D