I picked NJO, not necessarily because it's the best period or the most well written (it isn't), but because out of the options you gave I think it would adapt the best to a game format. It could pretty easily translate into a strategy game or a an action game, or something multifaceted like Battlefront, with ground and air combat with normal and special units. Honestly though I'm behind in my EU reading, by a lot, due to funds and time, so I can't speak for FotJ or even LotF firsthand, though I deliberately spoiled myself with Wookieepedia long ago. But really I'd prefer original stories more than anything.
I'm surprised the Dark Empire series isn't on there. I know Rogue Squadron already did it, but who wouldn't want to pilot E-Wings and take on World Devastators?