It depends, really. Melee played more smooth, and has more advanced little tricks. Meaning Melee plays more technical, and you have to focus on timing in Brawl. Brawl also made some techniques waaaay too easy, making them useless. Easy techniques are always useless! Now tether recoveries will only work on ledges, making them more useless, but easier, since they home in on the ledges. Why more useless? Because if you can get the ledge with a tether recovery, you can also do it normally. It was handy because you could fall for a little bit and grab the wall, increasing your recovery range greatly. We also got wall jumps, that are now automaticly performed when you jump while touching a wall. Easy, but totally sucking. Sometimes you don't want to do a wall jump, y'know.
Anyways, on the positive side, I was right. The Subspace Emissary takes about 10 hours to complete, and so far, I've got 4 hours of replay time, making 14 hours. Because once you complete it, you can go to any level with any character. Like going to the first level with Sonic and Mario as a team.
Stage builder is a little too simple and meant for every crazy idiot, but it does add alot of replay time. Most of the time I even make a level, and never even try it out in a Brawl match, and make another level after it. As for stage of the day....well....Nintendo doesn't have any taste. You only get small stages that make minimal use of the Stage Builder's properties. And that while Nintendo theirselfs made a few decent standard Stage Builder stages too. Isn't there any Japanese guy that can make good levels?
Even better is the total of characters. Sonic feels like too much spindash, but he's alright...seriously, no breakdance move for his Down Smash?!! No Sonic tornado for one of his special moves or slide kick for his dash move?!! ...anyway...this means more time needed to master 'em all, finish Classic and All star with them all, and more stuff. Although I never ever even played as Olimar or Ice Climbers before.
Oh, and online is more lame and on the other side better than you would have thought. How can you have online coop for Homerun Contest and none for the subspace emissary?! As for the other side, friend codes filling goes very fast, and playing with 1 of my friends on the same Wii against other people online was very enjoyable. I do wish they had stage builder stages for online if both friends had the same stage, though.
So yeah. The game rules. Something totally different from anything you'd expect on the Wii. It has its flaws and points where you say "aw..", but we all know thats because Brawl was overhyped. It would really deserve "best game 2007" if Brawl still counted for 2007, and absolutely "best Wii game" as titel. Buy it now.....or whenever its in your country.