Third Strike is the better game if you are willing to put time into it, but if you just want to play with friends who may have played street fighter 2 back in the day but dont have the desire to dedicate time learning the intracacies of a fighting game then you can't go wrong with ssf2hdr.
I think the games on demand version of super street fighter 4 arcade edition is pretty cheap. I know I can find physical copies around where I live for $20 new. If you can find that for cheap I would recommend that over both of them. --- Pokemon Black Tokiya FC: 0862 2942 5169