Well to be honest there are not that many flash games that are truly worthy for UMD release . But as a PSstore game there are plenty .
Lately I found a couple of 2D racers , sidescrooling racers . They where a bit awkward at first but soon after they got so addictive that I still have a couple of them saved on my desktop . A good example is Dirt Bike 1/2 ( the best ones from the series ) . They are simple , tricky and fun . Shore you can complete them in 3-4 minutes , but make 5-20 times as many levels , add a level editor and you get yourself an addictive PSN title .
But then there are more complex and longer games like N+ , games that have enough value in them to be released ( and thank god this game will ) on UMDs/carts .