It's clear that advanced techniques were removed to attempt to balance things out, but unfortunately, other circumstances break the balance (Snake? Snaaaake? SNAAAAAAKE!)
My preference on game depends on the character I'm using. My main is Kirby, so it's only natural I dislike Melee, because they nerfed Kirby beyond humane standards. SSB Kirby is awesome, though it's tougher to Kirbycide. However, I also like to use Roy (I never liked Marth, shoo) and that can only happen in Melee. There's obviously no Roy in SSB or Brawl, so Melee wins there. SSB one-player is repetitive and awfully easy, even on Very Hard. Melee's was most balanced, and Adventure > SSE (takes too long, can't use a single character all the way). Brawl's one-player is the toughest, but also the most annoying (Allies are just as they were in Melee, 1-vs-1 You vs. Giant Marth, etc., is just stupid/broken, All-Star is broken and doesn't really judge your skill too much, especially with characters that just take a lot of damage/are lightweight, yadayadayada) Brawl offers me my biggest lineup of characters I love to use, however. Also, Kirby got a big boost, and I can actually win in a FFA with it now instead of having to rely on Falco to do the job.
As far as stages go, Brawl wins with Lylat Cruise (thank goodness it's legal!), 75M (most fun stage ever alongside Saffron and Pokéfloats), and custom stages. However, many of the stages are also broke (Mario Bros.), annoying (Great Sea ugggggh), and simply unfair (Bridge of Eldin -- High % screws you no matter where you are; edge of stage = easy picking, middle of stage = boom). I miss quite a few stages from Melee and SSB, though -- at least I can *sorta* replicate them in custom stages, but I simply can't create a door that expels exploding Electrodes.
When it comes to tactics, I play very defensively, and I'm mediocre at combos, so Brawl's gameplay suits me best. I honestly find it easier to combo with Kirby in Brawl than in SSB due to directional throws, but that may also be because I'm older and better now (haven't played SSB with real people in quite a long time).
And of course, there's nostalgia. Metal Mario will always be #1, as will Giant DK and Master Hand. The only real Team characters are Yoshi and Kirby. Polygons > Wire Frames > Alloys. Melee made the mistake of killing board the platforms (I felt that it really tested your ability to move around / recover with your character) and then Brawl had to get rid of Race to the Finish (what's the point, seriously? I don't want to break targets twice in one game!). Individual BtTs were better, too -- Pit owns all five levels in the blink of an eye; he clearly needs tougher ones. Norfair fails compared to Brinstar as a "lava stage", Saffron > Spear Pillar (just a broken, hazardous stage -- Cresselia's Psycho Cut and Palkia's Spacial Rend are 100x more dangerous than Electrode's Selfdestruct), Jungle Japes > Rumble Falls (hate that place), etc. etc.
So... in my opinions, at least, Brawl wins in casual/fair gameplay, SSB wins in nostalgia and more balanced advanced play, and Melee's somewhere in between. I severely dislike the incredibly obvious tiers in Melee, though. I mean, did they really have to make Pikachu, Kirby, and Ness *that bad* because they were top class in SSB?
*awaits flame spam*