I generally tend to buy new games only after I've finished or lost interest with the previous ones, so this is probably the biggest backlog I've ever had (as in, games I haven't even started yet).
BioShock
Grand Theft Auto IV (including Episodes from Liberty City)
Victoria II
Hearts of Iron III
XCOM: Enemy Unknown
Mario & Luigi: Dream Team
The Legend of Zelda: A Link Between Worlds
Fire Emblem: Radiant Dawn
I've had Radiant Dawn sitting in the shelf since forever, because I've been (passively) trying to find a copy of Path of Radiance before playing RD. Some of the games I've bought/received only very recently from Steam.
As for the rest of the list, I blame Paradox games. Fuck you, Mount & Blade, go to hell, Crusader Kings II, stop taking up all my time, Europa Universalis IV. Why do I even bother buying new games if you won't let me play them?!
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