Ones or variants that haven't yet appeared in the games yet, I mean.
I'd like to see more concept, experimental, and other obscure aircraft like the A-12 Avenger II, X-32 JSF contender, X-44 MANTA, F-117N Seahawk, and YF-12 (armed interceptor version of the SR-71).
Drones like the Reaper and Fire Scout might also be interesting additions.
Additionally, I wouldn't mind seeing licensed use of fictional aircraft such as the Turbokat and Enforcer Jet from SWAT Katz, Night Raven from GI Joe, and F/A-37 Talon from Stealth.