I've gone to 2 midnight launches
1) Assassins Creed 3, nice atmosphere, everyone was friendly, and we got cupcakes
2) Black ops 2 (friend dragged me there) Children everywhere, crowded and people were angry
Two for me too (unless you count the release of RATM's Evil Empire album)
1) Halo 2 - It was at the EB flagship store at Universal City Walk. We got there "early" at 6PM and were still somewhere over #200 in line. Hyper kids bouncing around everywhere, a DJ playing the most godawful music ever composed at maximum volume, annoying G4TV camera crew repeated blasting their spotlight in our faces, didn't get out of there until well after 1AM. It was hell, but my Halo 2 hype got me through it, and kept me happy for a long time. I took quite a while for my hype to fade away and let me see the game as it truly was...
2) MGS4 - Much better experience, about 40 people in front of Gamestop in a mall, hanging out and chatting. But that was the last time I felt hyped enough to go to a midnight thing.