Yes umbreon and jolteon are particullarlly good pokemon. Though not the best. Jumpluff though is not getting near groudon anytime soon. And yes celebi is also a candidate for one of the best pokemon but groudon just seems to be useful for situations. I have to say I don't use groudon or celebi that much as I prefer choices that show more innovation in their training but they are both very good pokemon.

Also in GSC mewtwo could get quite the beating from a blissey. And on the subject of ho-ohs, let's just say my mates one got owned by my raichu (both level 100). I wasn't really surprised either. In the battle against my uber obsessed friend. I lost 2 of my pokemon while he lost all 6. Glorious days for beating such a gloat (cause of his legendaries). Although now I've taught him proper pokemon training he's fairly deadly.