jarrod on 11 July 2010
I haven't played all that many, but...
1. Portal (PC/360/PS3/Mac)
2. Metroid Prime (GC/Wii)
3. Half-Life 2 (PC/XB/360/PS3/Mac)
4. Half-Life (PC/PS2)
5. Metroid Prime III: Corruption (Wii)