I'm not a fan of artificial reverb, so I tend to use it sparingly and judge it harshly. I don't mind a well maintained plate for "genre" music, and there is even one spring reverb I don't hate, the AKG BX20.
The "best" reverb, in my mind, is one that can convince me I'm listening to a recording of acoustic ambience, and by that standard, the clear winner is the Quantec XLS. Nothing else comes close. If you're trying for realistic ambience, look no further.
Speaking of which, I'm trying to get mine fixed -- If anyone has any resources in this regard, please drop me a line.
I also don't mind the Klark Teknik DN780, which is very good for short reverbs, not so great for long ones.