The numerical order here is largely irrelevant
1. MTW/VI
2. Civil War Generals II -- especially the MP, and this one was great for modding. AI was weak, but I'm partial to good Civil War games.
3. Red Baron 3D -- Excellent campaign.
4. Spaceward Ho -- Laugh, but it is a fun little game, and can be extremely challenging if you set it up right.
5. SM's Gettysburg
6. SM's Antietam
7. Lords of the Realm II
8. STW/MI
9. Tie Fighter
10. Civil War Bull Run

IL-2 series doesn't make my list simply because of the problems with uber laser cannon gunners, lack of an interesting campaign, and problems with historical balance. I gave up after FB...too many immersion killing moments in what could be the most immersive sim ever. If they could just graft on RB3D's campaign...