Hey, don't get me wrong, I like Captain Falcon, but he's definitely bad in Brawl. Even Ganondorf actually combos and kills better than he does, which goes to show how much the physics engine screws with Falcon. As much as I hate to admit it, he's really the ultimate bland and ineffective character in this game. He doesn't have anything particularly special going for him, set aside running speed which no longer helps him get any godly combo setup.
I mean come on. NO COMBOS. NO RELIABLE KILL MOVES. There are next to no real combos in Brawl due to the way the shielding and air dodging system works, plus there is like no hitstun in Brawl (don't get me wrong, combos exist, but there are only very very few that can be used reliably). Captain Falcon never really had any single attack that could be used by itself as a kill move. He was all about comboing into killers, which he and most other characters can't do in Brawl. Most importantly, you can't combo into the Knee anymore. The reliable attacks that Falcon does have kill at much much higher percentages than average, and Falcon's actual kill moves are all situational to the extreme due to the lack of any combos. His Smash attacks are still too slow, the Knee can't be comboed into, the D-air doesn't meteor reliably, things like that and other attacks that he can land on enemies are generally too weak to actually kill.
His range and priority overall is worse. Noticably, it's harder to grab and land D-airs on opponents, plus you can't L-cancel, so no D-air approaching. You can't approach with the N-air due to the fact the kicks have a more narrow hitbox. Basically, Falcon is a lot worse at approaching.
Captain Falcon still has the worst special attacks in the game....sadly. They improved them in terms of recovery slightly, but that's mostly it. Now he gets no combo setup from the Raptor Boost (which doesn't kill anyway until like past the 200% mark), he can't combo into the Falcon Punch either. He can't do Falcon kick recovery, although it's just a tad better as an attack (I think it has less lag, and slightly more knockback, eh). The only special attack of his which is definitely better without nerfs is the Falcon Dive, which does have more range and power, but not by too much.
What is still good about Falcon is his U-air and B-air. Those are still good attacks. U-air maintains it's good range, and while you can't juggle with it much anymore, it's now more of a very high % kill move (as I said, Falcon's reliable attacks kill at much higher percents than average, while his true kill moves are unreliable). The B-air however has pretty much remained the same in Brawl. Fast, strong, and low lag. The non-sweetspotted Knee causes tripping. Plus, Falcon's U-smash oddly enough is better due to his lower traction so he gets good distance from canceling a Dash with a U-smash, and the two hits land more easily, despite the hitbox being overall smaller. Stutter stepping helps improve Falcon's F-smash to a minor degree. Plus, I personally think that Falcon's jab combo is better. While doing the Gentlemen is now pointless, the rapid punch combo lands a lot more effectively which can get you a free 20% on the enemy.
Still, he doesn't have anything really special going for him, and he lost essentially everything which made him good the previous games.