Are there any N-Gage emulators already out there? With source included?
To be honest, even if there are, and even if it's possible, you're unlikely to see one on the 2X simply because there's likely very little interest in it.
While the N-Gage has an ARM9 processor just like the one in the GP2X, it also has rudimentary hardware acceleration and a pile of proprietary cell phone hardware.
I believe we discussed the practicality of porting Series 60 a few months ago.