The WildPalm doom is old and crappy. There is a newer doom port called c2doom. It uses the original WAD-files so you can play doom and doom2 with it.
http://koti.mbnet.fi/mertama/
It works on all s60 phones, like 3650, 6600, ngage etc...
I'm thinking about buying gp2x, but my ngage is a pretty...