Well I guess it could be done in two ways:
1-The most likable team for myself; which would more or less be the top 6 favorites. In which case, Greninja, Krookodile, Gliscor, Sceptile, Heracross, and Charizard. I'd like to see something from each gen on his team so more a matter of favorite from each gen I guess.
2-The most likable for the majority of people. Which is pretty difficult to determine regardless, lots of factors to take in but nonetheless:
Pikachu-It's overall a nice Pokemon, has it's quirk of liking ketchup, makes Pokefaces from time to time. It was even stubborn at the start. It doesn't really do anything personality wise that would make most roll their eyes.
Bulbasaur-I feel most people would like the fact it tries to bring the peace. However, it didn't really come off friendly for the most part, so if anything, it could be seen as too serious.
Charizard-Pretty much it's whole story. Started out with a sob story so people had to feel sorry for it. It evolved and became kind of annoying, but eventually it had another heart warming moment and it became more likable again. The breathing fire on your face is probably not much of a likable quality though if you're own the receiving end.
Muk-? I mean, so long as it's not body slamming you, then it's probably nice seeing such a thing with loving qualities.
Totodile-It's always smiling and dancing, I'm sure most people would be happy around it.
Sceptile-Got the cool guy attitude, but as such, not too much on the friendly side.
Infernape-Mainly due to its story. Feel sorry for it, and then be proud it was able to prove itself.
Buizel-Another cool guy, again not much for friendly.
Gliscor-The crybaby part I don't feel would be likable to most, but it's growth I feel would be liked. Plus it has its cute quirk of winking and sticking out its tongue.
Snivy-Cool girl attitude. Also had some peace making qualities. But again, not too friendly.
Leavanny-It's a pretty happy Pokemon(Not as a Swadloon), it'll make you a leaf hood, who wouldn't want that.
Krookodile-Another cool guy, and again, not too much in terms of friendliness. It does have the crybaby aspect to it when it loses its glasses but I feel most people would just find it amusing or feel sorry for it instead of getting annoyed by it.
Squirtle-It was pretty friendly, not much really sticks out but you probably wont be annoyed by being around it.
Lapras-It was a baby but not a crybaby, the kind of baby you want to protect. It wasn't gleaming with personality, but it seemed pretty likable anyways.
Greninja-Cool guy, not too friendly.
Hawlucha-Cool guy, kind of friendly. I feel most would enjoy seeing it's flashy personality.
Goodra-It's just really happy.
So I don't know. If I had to pick 6 from there(And one from each gen again), probably be Pikachu, Totodile, Sceptile, Infernape, Leavanny, And Hawlucha. Balance of cool, happy, and nice.