Personally, I think that if you don't at least
try them all, you're not getting your money's worth.
But if you're just looking for a straight-up popularity contest, well... it's not a perfect sample of the whole game, but the statistics page on CIT is good enough for a rough approximation...
8103 Scrappers
6856 Blasters
6429 Controllers
5840 Defenders
5536 Tankers
1390 Peacebringers
1194 Warshades
As for villain ATs:
4459 Brutes
4353 Masterminds
4272 Corruptors
2601 Dominators
2350 Stalkers
1105 Arachnos Widows
1103 Arachnos Soldiers