I'm interested in solitaire games with the following criteria:
1) MUST be soloable
2) MUST have a progressive campaign where the outcome does matter from scenario to scenario.
Games I'm interested are Hornet Leader and Descent where you play several missions in a campaign and where your group either progress in power/skills or wither and die in a mission.
Doesn't descent require an overlord?
Moving along, in addition to the Hornet/Apache/Phantom/U-Boat Leader, there's the Field Commander Rommel/Alexander/Napoleon/Nimitz games also by Dan Verssen Games.
Does a game that isn't really broken into discreet scenarios count? Something like Silent War/Steel Wolves?
How about the Ambush! series. I don't know enough about them to say.
Those are the ones off the top of my head.