1. Team Fortress 2
Team Fortress 2 is damn near perfection when it comes to core game mechanics. While weapons do break how the game was intended to flow, the rock-paper-scissors matchup of classes and weapons never get old. The system of Achilles' Heels, where each character is one and has an opposing class that is one, is something that really shines when you are in a server that gives a shit about team balance. Scouts hunting down Medics, Pyros getting that fire damage on said scouts, Snipers bodyshotting Pyros, Spies backstabbing Snipers, etc. etc. While the system has gotten muddled with weapons breaking the links, at the end of the day, the 9-class system is almost perfectly balanced. It doesn't hurt either that the weapons all feel responsive, the gameplay loop it generates for each of the 9 characters feels fun, and my characters look dapper as fuck in their virtual clothing.
2. Super Mario Galaxy
I was a Nintendo kid growing up. My childhood was the Gamecube, the Gameboy, and the Wii towards the end of it. While my peers had Playstations and Xboxes and the like, I was stuck with the "kids" console. And I never felt satisfied with the systems I had. There was never a game which made me think "I love my Wii/Gamecube/Gameboy." Cue Super Mario Galaxy. Super Mario Galaxy was platforming perfection. From the moment I started playing it to the moment I got that 121st star as Luigi, I never, not even for a second, stopped loving that game. Between the comets, the interesting locales and the varied level design that followed, Super Mario Galaxy was something spectacular in every facet.
3. Uncharted 2
Eventually, my parents got me a PS3 after I had been whining to them for months about how cool Gran Turismo 5 looked and the sheer awe that FF Versus 13 inspired in me. One of the first games I played on the system was Uncharted 2. Some backstory: before I got the PS3, I used to pretty much beg my family to go to Target. And every time we arrived there, I just yelled bye and sprinted to the gaming section. The PS3 there was almost always free and the only demo I even touched was Uncharted 2. I played that demo at least 5 or 6 times through and through and felt a need to play the game in its entirety. Eventually, a friend loaned it to me and I got hooked. The first time I played the opening of the game, I was struck by how damn pretty everything looked. It was one of the first games that really just gripped me and never let go. Everything about that game is great; the way the game mixes high-tension action scenes with slower moments, the dramatic turn in Tibet, the gunplay, and the scale of the platforming. Uncharted 2 is one of the games I don't hesitate to play through multiple times and considering I've already beaten it on Crushing, I might have to acquire a PS4 to play the collection's version on it as well.
4. Spelunky (flash version)
I love this game, and I hate. I want to strangle it to death in an alley, and I want hug and kiss it and tell it sweet nothings. I fucking hate you, but I love you, Spelunky. After I moved to India, I didn't have time to game. Power cuts, shitty internet, and a lot of schoolwork meant I never got to play video games. Then one day, I stumbled on an article promoting Spelunky as a Chrome attachment. I was intrigued. I downloaded it, entered the door, and promptly died. Over and over and over and over. See, I thought Spelunky was just another mediocre platformer. So, I was surprised when layouts started shifting, items were being introduced, and the spider monsters started appearing. Spelunky was my first rogue-like and I'll never forget my days of zoning out to music & trying to beat the damn thing. When I finally did beat it, after 1000 tries, the sense of elation and accomplishment I had in that moment is something I fear I will never experience again. Spelunky is perfection, brutally unfair perfection but perfection none the less.
5. GTA 5
Fast-forward to summer of 2014. I got accepted into college and was wiling my days away in an empty house as my parents and sister were doing things. I had convinced my mother to buy GTA 5 for me when she had gone to California for a trip, and I hadn't even touched the game till now. I popped it in, and promptly had to download what was gigs of data on 100 kb/s internet. I waited the requisite 8-10 hours, and then had to shut it down because my parents got home and they wanted to watch some TV. The next morning, I finally got to play it and when I did, I was blown away. I know GTA 5 gets a lot of shit for its "satire", its depiction of women, etc. etc. and rightfully so, but Rockstar just knows how to build worlds that feel inhabited, that feel alive, that make every second you spend in them feel like reality. I love just driving around the island, blasting the radio, and just looking at the cars pass. The heists were things of beauty and the build-up to each one though tedious felt like a realistic part of the process. The game is something of a masterpiece in its world building, in its detail, in its ability to make a city come alive. Its just a shame everything else can't match up to that high bar, but even then everything else is great.