SSBB has 35 characters.
SSBM has 26 characters.
To be completely honest, this sold Brawl as better to me over Melee instantly.
Why you might ask? Because I used to play Melee for hours and hours and I got so damn good, and then I'd go to play with my friends and we honestly couldn't play it very long because we'd run out of fun characters to use. I feel that Brawl's addition of characters and modifications to characters gives a much diverse fighting experience... and adds use to characters I'd never touch before. Here's some things about Melee that bothered me.
~Honestly~
-Bowser was trash.
-Yoshi had so many shit-sides.
-Mew-Two was honestly a one or two-trick pony.
-Luigi... sucked.
-Young Link was a joke and was just a weaker Link.
-Pichu was dumb as hell to have because Pickachu was the same thing but stronger and didn't hurt himself.
-Ganondorf was a carbon copy of Captain Falcon that was slower but stronger.
-Roy was an overpowered asshole, and Marth was an underpowered Roy copy that was really fast. <--- That's stupid.
-Falco and Fox... I can't really put any exact stat on it, but they were the same thing. Fox fell harder and faster, also his "third jump" was much longer. Falco attacked faster and did only a little bit different damage.
-Dr.Mario and Mario... I don't really want to bash it cause I loved Dr.Mario as a character, but they had the same movement and attacks. Only difference really was a little speed, damage, and the sideways smash.
^Most of those are just my opinion so don't take offence and say I'm wrong.
Brawl fixed all of that, and added more characters. From what I've seen, nearly every fight can be fair and is more based on a player's skill rather the character match.
Melee, Bowser/Ganondorf/DonkeyKong vs Sheik... I swear to God, Bowser/Ganondorf/DonkeyKong could not win even if the player using Sheik had only gotten the game yesterday.
Melee again, Roy vs Anything... Seriously, you can win by just hitting the C-stick left or right and dodging, it's retarded.
I know there are a lot of other views/opinions/feelings on these two games, I'm looking forward to having a good convo on this one.