People were talking about higher resolution screen for ages. You weren't the only one comparing resolution when SGS2 came out. Even the nexus had higher ppi levels near to IPhones. And if your carrier had a return policy, maybe you could return it for the Nexus (assuming screen PPI is the most important thing for you)? But there are still features of the SGS2 that makes it worth it IMHO.
I like the HTC One X too. Pretty good specs. But what kills it is the non-replaceable battery as well as memory that cannot be increased with a microSD. In that sense, the SGS3 is a better option for me. Either way, I will happily keep my S2 which I have been using for 9 months now and wait until my 2 year contract expires (at least).