First, don't buy any $30-$60 games, way out of price for what they offer. If you plan to get any, wait for sale. Including the games everyone mentioned above. If i had to recommend some games, Blaster Master Zero and Mighty Gunvolt is eshop only but $10, Puyo Puyo tetris is $30 on eshop but $40 retail. Still I would wait for price drop. Shantae 1/2 Hero and wonderboy dragon's trap is $20, five dollars less it be better, shovel knight as well is $25, five dollars less and it be better. There is tons of neo geo arcade ports.... Ignore them unless you like $8 neo geo games with no online modes. Azure striker gunvolt striker pack will come out agaust 30 for a estimate of $30-40 (Price not announced yet) Fast Racing Neo i hear is good, but never played it, maybe consider it, and so is I am setsuna, Cave story + also, the price once again is a issue.
Sorry is hard to actually say anything worth while without mentioning prices. I'm sure is actually games worth paying that much for but from what I seen i don't believe so.