Wing Commander - PC, SNES, Amiga, FM Towns, SegaCD, CD32, 3DO, Macintosh
The Secret Missions - PC, SNES, FM Towns
The Secret Missions 2 - PC
Wing Commander II - PC, FM Towns
Special Ops 1 - PC
Special Ops 2 - PC
Wing Commander III - PC, 3DO, PSX, Macintosh
Wing Commander IV - PC, PSX, Macintosh
Wing Commander Prophecy - PC, GBA
Wing Commander Secret Ops - PC
Privateer - PC
Righteous Fire - PC
Privateer 2 - PC
Wing Commander Academy - PC
Wing Commander Armada - PC, PC9821, FM Towns
Proving Grounds - PC
So, I count 34 off-hand... but that's not including Win9x ports (4 -- KSWC1-2, WC3, WC4 and Privateer 2) or weird little extras like Origin FX (which has several WC modules).