Wow, there are a whole lot of underserving games on that list...The worst is that I keep getting the few worthy games places off against each other...Half life vs Dues Ex? They would both be looking at top 5 spots if they didn't get squared off against each other so early.
OK,
Morrowind
Warcraft 3
Half Life
Heroes of might and magic
Duke Nukem 3D
...Duke nukem definately only got their because of the easy tree, half life and warcraft each knocked out a plethora of titles that deserve to be far higher ranked than they were (max payne, dues ex, crysis, doom, wolf 3d, guild wars etc).
*edit* I'm impressed by how high Morrowind ranked. It was hardly a broadly appealing game so I wouldn't have expected it's popularity (despite it's utter brilliance).