Mew, Celebi, Jirachi, and Manaphy all have equal stats, so in terms of best moveset variety, Mew is obviously the choice variable Pokemon. Of course, each has their own exclusive moves, so it all boils down to nature, EVs, and your own preferences.
As for the anime, well, I just plain hate the anime since it's just hundreds of episodes of filler. As with the game, it all depends on experience in battle.