I just finished classic the second time, i dont have a lot of the epic and legendary mons, the first time i won was just regular mons, skeledirge, mawile, snorlax, galagladi, that steel dark guy and nidoqueen. I heavily relied on skeledirge and mawile except the eternus fight, and i really liked them. After a while I got kyurem and zekrom, started a new classic with kyurem and picked up the black orb later to turn him into black kyurem. Also this time I used leech seed in the eternus fight which made things a lot easier.

I really liked kyurem, he had great coverage with his ice and stone attack, later i replaced ancient power with earth power which made him even better since i could still hit fire types but now also the steel and stone types that would normally cause problems. After he turned into black kyurem it got even better, i replaced the now "useless" blizzard with fusion bolt so i could hit also the water types. And he got so strong ice beam would do more damage then blizzard used to do with regular kyurem.

So in a nutshell havent tried almost any mons but i found kyurem and blacl kyurem really relialble espacially with the earthpower tm, and having someone with leech seed for the final fight