lets see... considering i've only played Brawl at Turndawg's house, i'll have to give a pretty rough estimate... oh, and i'm going to 5 because i want to...
1.) Captain Falcon: Need I say anything? Captain Falcon has great speed, awesome combo-ability, and some good specials to boot, although Falcon Punch leaves you REALLY open in Brawl... His Final Smash is incredible, and he's got great recovery time IMO. That made it possible for me to avoid all but one grenade from Turndawg's Snake one time. I was happy with myself.
2.) Ness: My favorite char. from Smash 64, Ness is an all around good character. Now that I've gotten good at controlling his PK Thunder, I'm not limited by his jumping abilities. He's great for edgeguarding, and his combination of short/long range and physical/psychic moves makes him great. Not to mention, PK Flash and his Final Smash are frickin awesome when they hit.
3.) Pokemon Trainer: Another excellent character, and one of the few new characters that really impressed me. The versatility of using 3 pokemon gives you an edge in battle. Charizard is great close range and has good recovery, although he is a tad slow. Squirtle has good speed and decent long range, but his physical strength lacks a bit, making it difficult to Smash-kill with him. Ivysaur has decent speed and a nice combination of short and long range attacks. However, Ivysaur's jumps and recovery move are ok at best, making edgeguarding an easy task against him.
4.) Lucas: Since I favored Ness in Smash 64, I loved Lucas. Ness's close range attacks are replaced with many more psychic and long ranged attacks. Lucas seems to have better knockback damage than Ness, especially his PK Fire. However, Lucas is below average in close combat, and seems to be a little easier to kick around than Ness. Overall an excellent character, but Ness is still better.
5.) Luigi: Luigi is a great classic character for me. He has great potential for combos, especially with his improved tornado punch. The Flaming Coin Punch is harder to hit people with than in SSB64, but when combo'd with the Final Smash, makes for easy kills. The Funky Color Land Final Smash gave me a good laugh, and I like Luigi better than Mario anyway. His dash-A move is more effective than Mario, and although he is a bigger target, he has better strength. Besides, I'm a fan of the underdog: Luigi is always stuck in Mario's shadow. FIGHT THE POWAAH!!!
So there's my top 5. They could shuffle around in order once in a while, but they are my favorites. (Oh, and if you dont like me because I picked 2 "clone" characters, then my next choices would be Samus or Pit... [->B] "HOYIYIYAAH!!!")