UPS
-It's Super Smash Bros.
-Subspace Emissary
-Pit, finally
-Some unique surprises such as R.O.B., Pokémon Trainer, and Olimar, although Olimar isn't too good IMO.
-Wario, finally
-Dedede, finally
-No more Roy (though I did favor him over Marth, I just disliked the clone factor)
-3rd party inclusion. I haven't quite unlocked Sonic yet, but I probably will within the next day, but Sonic is a great inclusion. It's like a gamer's wildest dream come true. Also Snake is actually quite strong. I know I was skeptical at first, but Snake isn't bad, though I still am eh about Snake's inclusion due to the character himself.
-Awesome stages. Mario Bros., 75mm, etc.
-The music is absolutely amazing. It's something I could listen to all day everyday, and if I get a new mp3 player, I just might do that.
-Awesome new items. Dragoon is absolutely genius, then you also got the soccer ball, the golden hammer, and so much more.
-Assist trophies are brilliant.
-Masterpieces. Great way for the newcomers to Nintendo to find their roots.
DOWNS most of these are easily overlooked
-Meta Knight is absolute trash, the worst fighter easily.
-New Pork City is a horrible stage, I hate using it.
-Clones. They're not necessarily bad, but it tends to be annoying that there's generally three versions of Fox, each slightly altered.
-Stickers, who's really going to use them? Sure some will, and it's not necessarily a bad thing, but I just don't see when I'll ever find myself using any.