I much prefer Melee to Brawl, the faster pace just feels better. That, and I think a lot of the Brawl items feel overpowered (don't get me started on the Final Smash, always turn it off)and that stupid trip mechanic is terrible. Sure, Melee had tough challenges, but that was kinda the point. Anyway, you could easily just play the main melee with easy bots until you got better. As others have mentioned above, it was simple to learn, hard to master, and that is a rare and beautiful thing. Besides, I loved the more individual challenges in Melee, expecially the target smash, which was different for each character and usually required use of most if not all of their abilites.
Besides, I think SSB is already considerably simpler than many other fighting games where each character has umpteen combos; SSB gives you normal, specials, and direction and lets you go nuts. That's why I love it.