Mine in no particular order of preference.
1. Graphics. (Vital for immersion).
a) Aircraft detail accuracy
b) Map detail and accuracy
c) Sky and horizon merge
d) Sea
e) Cockpit and crew positions
f) Cockpit lighting/shadows movement
g) Cockpit internal reflections on canopy
h) Sun
i) Detail and accuracy of ground objects
2. Flight Model
3. Damage Model. (The best I've seen in a Flight sim).
4. Bomb explosions
5. Mission Builder (Very similar to il246).
6. Very large maps
7. Sounds
8. CEM
9. Vibrant Community
Best Regards,
MB_Avro