Okay, I will not blow my top on this one, because it is LOGICAL.
Let's look at the ups and downs of each 'mascot'-
Mario- Pro- Widly popular with childer and adults, has a LONG series of games, 3 cartoon series, 1 movie and 'promoter of Dolphin'
Con- A bit TOO popular, so many games, 1 movie (Good or bad..)
Crash- 4 good games, Funny commercials (IMO), Mascot of PSX
Con- Not that many people know him, advertisments (Insulting Nintendo. I liked it and hated it.), Dosen't talk
Sonic- Pros- Most recognized, 3 cartoon series, loads of sucessful games, the Chao
Cons- Sonic Underground, hates Mario
Lara Croft- Pros- Widly popular, boobs, 5 games (1, 2, 3, 4 and GBC), smart, strong
Cons- Boobs, 5 games, guns, boobs
Personally, I think They're all great. Don't get me started with Pikachu...