Yeah, I second that. Mario is a fairly straightforward character with a lot of up-front power and some pretty decent depth. Other great choices:
- Yoshi
- Ness
- Captain Falcon
- Sonic
And if you want to go a little deeper:
- Shiek
- Pikachu
- Zero Suit Samus
- Rosalina
- Diddy
The above five are considerably harder to just start right into than the five named at first for various reasons (Pikachu and Shiek have to fish for kills and have some tricky combos, ZSS relies on her combo game and her grab is really weird, Rosalina has odd Luma gimmicks that can take some getting used to, and Diddy requires an understanding of items that is a little hard to get used to), but are also definitely viable, and can be a blast to play.