Well, ngage too powerful? No man, the problem is not that.
Ngage runs an ARM cpu 108mhz. one custom gfx chip (16bit color handling) that only does the work to execute strings and codes...so basically, is not very complex in architecture terms. Sound chip is also a low-media type, the gp32 is too much powerfull than it. The problem, talkin about emulation , is the OS: symbian , in fact, it's hard to emulate since nokia and symbian currently SDK dev. tool it's not that deep into resources...and no one is using it right now lol. Anyway, u can grab the sdk dev tool from nokia site. Emulate an N-gage, in other terms, needs the emulation of the OS itselfs. so it's hard to say that in the near future there will be an ngage emulator....for now, there is only one and it's for that java games: It's called Game Station and is very kewl.
EDIT: j2me emulator, as i say, it's available to buy. It runs nearly all series40,60 games whitout problems. BUT ngage games r symbian ones and uses the architecture and scalability of the OS (Symbian 6.1) that is not java. that os can handle , if well ram equipped, 3D games whit no problem. Take a peek to the first dumped ngage games: when u open the rar is only system folders, dll and exes...encrypted, all of them--- talk about encryption, nokia done a good work itselfs....but hacker already done a better one. lol