I have played 7 - X-2, personally I thought that 8 and 9 were pretty weak...but thats just me. 7 is the default best and I was really impressed with 10. 10-2 was about the most flaming game I have ever played...so stupid.
But yeah other than that I am playing
Ace Combat 5 (PS2) Fire Emblem: Path of Radiance (GC) AOE3 (PC) already beat it. Civilization 4 (PC) very very addictive