I'd put ESB above the other two, which are rather equal in my opinion.
As for TFA being the best one yet, I do see it as a possibility, but there's an equal possibility that it could be the worst. I'm pretty sure I will at least enjoy it, if not love it, but I'm not going to get myself so hyped up for it before it comes out that it totally destroys me if it sucks.
That said, I'm definitely excited for it, and I've even fallen for the hype and gotten myself some merchandise and may very well get more.
Even if the underlying story isn't as strong as the OT, I could still easily see it being the most thrilling, fun, and viscerally exciting SW movie there's ever been. Especially when you factor in JJ's dynamic style and the sheer fun of seeing Han, Luke, Leia and Chewie on screen again.
Unless of course the story is so wrong-headed from the start (as was the case with Into Darkness, IMO), that the movie just never manages to recover from it. But given the involvement of Kasdan I don't really see that being a problem with this movie.