Wow, this is really close.
In the end I had to go with City, just barely over Alien.
When I got City I realized that while, at first, there were no huge standout tracks to me, outside of the Cop Shoot Cop cover, which I think SYL did a million times better than the original, and I love the original, was just such a strong album. I don't know what it is with that album, but song after song it blows me away.
When Alien first came out it was my favorite. From there it did wear on me a bit, but very quickly picked back up for me. It's a very close battle between Alien and City. In fact, I think Alien contains more standout tracks on it with Shitstorm, Zen (which holds a very special meaning to me after listening to it multiple times after the suicide of a friend of mine), and so many other tracks, and I'm one of the few that loves Info Dump as well. However, that starts where the album loses it's ground to City (although not to almost any other album out there). Info Dump and most of the rest of the album are things that I almost have to listen to at different times because of how different they are. It's like I'm in the mood for them at different times. However, even with a couple more Alien tracks instead of Info Dump I think I like City more in that Info Dump is at the same time another reason I like Alien more since it is something different it gives me something from Alien that I'm always in the mood for. I know it doesn't make much sense, but yeah, City is almost the holy grail of music for me while Alien is pretty amazing itself.
"And let us dream now, the impossible dream, of a math professor" - SGM