I particularly enjoy these Sonatas, they're Beethoven in transition, very interesting. The G major isn't played a lot, it's underrated IMO. It and the Eb are overshadowed by the famous "Tempest", but the Eb gets more playtime than the G major, probably because it's more of a showpiece. The G major is very difficult, but not in an obvious way, which may be why it's neglected compared to the other two.
My favorite is the d minor, the "Tempest", actually my favorite of all 32 Beethoven Sonatas. I like the other two equally. In terms of difficulty, from hardest to easiest I woulld rate them....
1. #3 in Eb
2. #2 in G
3. #2 in d minor.
Check the difficulty ratings in the sheet music section here, they might differ from my opinion. Also I just played the "Tempest" so my opinion might be biased. After playing the 1st mvt. development of op.2 #2, there is nothing in these sonatas except the finale of op. 31 #3 that should scare you...