Vaporeon>Espeon>Jolteon=Leafeon=Umbreon>Flareon=Sylveon>Glaceon.
The first five (and Sylve) have been immensely useful in in-game playthroughs, I just like Vape's tankiness and power more than the others. Haven't bothered with Flare for some reason, and Glace comes waaaaaaaay too late to be useable in-game. The only reason Sylve is so far down is because I'm not a fan of its design. I don't outright hate any of them, though.