I could probably come up with a couple hundred at least. My backlog is huge and it keeps getting bigger. Fortunately, I don't have much interest in many newer games, so I might be able to make a dent in it.
Personally, I would like to beat a lot of the classics from various eras. I'm not that much into platformers and RTS games, so that narrows down my list a lot. Then again, I'd like to get more into CRPGs, and those often require a big time investment. I'm also interested in games known to have great stories or epic scope.
I'm a giant science fiction geek, so games like Starflight I and II, and Star Control come to mind.
I love the Fallout universe, so I'd like to try out Wasteland. I also need to finish Fallout 2. I was really into it for awhile, but I got frustrated after my car got stolen and I lost some items that are needed to beat the game.
One thing that has stopped me from playing or beating certain games is laziness on my part. I'd like to tackle some text adventures like Planetfall, as well as some classic CRPGs. However, I've been to lazy to break out a notepad and graph paper, which I'd probably need to beat them. This also applies to a lot of strategy and simulation games. I love history and old wargames sound appealing, but when I get home after a day at work, I'm usually not motivated to open a 200 page manual.
I also find simulation games (submarine and flight, especially) very rewarding, but I don't always have the energy to tackle the learning curve. It's worth talking about what I find rewarding about these games. I obviously like gaming, but sometimes I feel like I could be more productive with my time. Now that I'm an adult, I don't have as much free time as I had as a kid. I find it hard to justify putting in the time to finish a game that takes a hundred hours, when I have other hobbies like music that I'd like to put more time into. I don't feel as guilty playing simulations because you can learn a lot from them. From submarine sims, I've learned a lot about sonar and other aspects of submarine warfare. From flight sims, I've learned a bit about flying and playing WWII flight sims on full difficulty gives me a huge rush from it being so challenging.
I'd also like to get into more educational games that aren't for kids. This also has a lot to do with me getting a bit more out of it. I don't think they have endings, so it might be a bit off topic, but the old Creatures games come to mind. Beneath the cute graphics are some pretty impressive biology simulations.
To wrap it up, here are a few others that come to mind.
Jagged Alliance 1 and 2. Squad based tactical games are underrated imo.
Skyrim. I have started it a few times, but never finished it. I didn't get into it as much as Oblivion, but I'd still like to finish it.
The X-Com series. I've beaten the first one, but I still haven't tried out any of the others.
Space Quest 6. I've beaten the first 5, so I would like to beat the last one.