I don't play much games anymore, so I mostly focus on the games that have the best NP payout in terms of points and difficulty. There's a petpage that keeps track of the new ratio's every month:
http://www.neopets.com/~zip_lightfoot (might take a couple days to update, although April was really fast
)
I still play a couple of my favourites, Kass Basher, Shenkuu Warrior and Crisis Courier (the last one has actually become attractive to play again), but besides that, the only one that's worth playing this month (compared to last month) for me is Maths Nightmare.