I reckon all Smashes are good in their own way, but 4 has, in my opinion, the best roster.
Agreed, even taking into account that they cut my favorite character. This is the first SSB where I find myself not just using 1-3 characters and only touching the rest for Classic/All Star/other unlockables. Sure, I still have my top few, but I find myself using others for fun and it took me a lot longer to settle on mains this time around. That's not even considering the actually pretty awesome and unique newcomers this time. Yeah, there's Lucina and Dark Pit, but there's also characters with their own unique feel or quirks like Robin, Shulk, Rosalina, and Duck Hunt. A few characters who I didn't care for before have grown on me this time as well, including Mario and Ganondorf.
As for best overall SSB, that's a tough call, especially since I haven't played Melee in years. I'd say I like SSB4's overall feel, but with items on and more than two characters going at it, I feel like Brawl and Melee (from what I can remember) do it a little better without going to overboard. Though, not counting the original, SSB4 has my least favorite selection of single player modes. Events, 3DS Classic, and the Orders are fine, though.
There's also the fact that after Melee, I usually only played SSB solo. Sure, I've played Brawl and SSB4 with my brother before, but that's around when he mostly lost interest in Nintendo games, plus my Nintendo fan cousins moved farther away. So naturally I poured more hours into Melee than Brawl or SSB4, but that's because I played with more than one person. As for Brawl and SSB4, I feel like I've played 4 slightly more. It does get dull on your own, however. I wish at least that they had the 3DS Classic mode as both Classic modes. I've poured a bit of time into that and Orders (though not so much since they cost coins).
I don't mind Smash Tour, but I feel like it has too many flaws to make me love it as much as Melee Adventure Mode. The entire random final match idea is weird- it should just be a normal match plus the power ups from the Run. It's also a pain that you have to have four players to do it, and it can get kind of exhausting after one or two runs.
EDIT: And I'd say Melee had my favorite stage selection, though 4's has grown on me (for both versions- probably more Wii U's, though).