I can't believe anyone would think ROTS is better than ANH let alone on par with ESB. I think it's debatable that it's better than ROTJ but the characters in ROTJ are much better as is the dialogue and that goes a long way. The only bad thing about ROTJ are the Ewoks, there are plenty of bad things about ROTS. My rankings:

1. ESB
2. ANH
3. ROTJ
4. ROTS
5. AOTC
6. TPM

Although if you take Magnolia Fans' Balance of the Force I think that is better than ROTS, he did a fantastic job editing the movie to make it much, much better.