Right now, Rift looks the most impressive imo on max settings. But I don't think it'll age that well. I recently had a look at Lotro again after it went free to play and I was disappointed by the graphics - I remember it looking great when they upgraded the client (can't remember exactly when - 2009?), but it really has lost its lustre in my view.
Wow's art style is fantastic. The character models (esp. human - real eyesores they are) are poor, but for a game over 6 years old it has impressive and very scenic landscapes. That's one thing TOR is getting right, I think. I can see that it'll still look distinctive in 5 years' time, whereas by then Lotro, AoC and Rift will look horribly dated.