I don’t think you can use FS2004 scenery with the CFS3 scenery. The sims are very different (in some aspects). Maybe it’s possible to use FS2004 aircraft, but the scenery??

Anyway, you could try IL-2 or Pacific Fighters. Great game with great graphics and realistic gameplay. I have IL-2, Ace Expansion Pack and Pacific Fighters combined and it’s great! I’d really recommend it!