29. Slaves to Armok: God of Blood Chapter II: Dwarf Fortress (Bay 12 Games, 2006)
I was never a big fan of shoot-em-up games; many of them start to feel very samey to me after a while, not to mention the fact that they feature one-hit deaths and swarming enemy patterns that are generally extremely trial-and-error based and require spot-on precision, and I don't really have the patience for that kind of thing. Tyrian 2000, however, is more my speed. An updated re-release of 1995's Tyrian, the game also features a lot of elements not normally seen in the genre - an in-depth storyline told between stages, a wide variety of customizable ship parts, weapons, sub-weapons and ship types, and even a pretty good sense of humor as you play through various minigames and collect giant fruits for points and have the option to pilot a ship that fires bananas and hot dogs at its enemies. Of course, the colorful graphics and sweet soundtrack also help, as does the fact that you actually have a health bar (in the form of a shield meter that regenerates over time and an armor meter that can only be restored via powerups). It still manages to be quite a challenge, but it's one that I can get into. Tyrian 2000 is a standout title and, for my money, the best top-down shmup ever made.
24. Worms: Armageddon (Team-17, 1999)
Just one game in the long-running Worms turn-based warfare strategy series, and the one widely regarded as the best in the franchise. Unlike many of its sequels, it gives players the option to have teams larger than four worms (six or eight, depending on the number of players in the game), allows for custom team voices and terrain to be imported and has just the right blend of weapons, gadgets and options to make for lengthy, yet engaging online battles - from airstrikes to poisonous skunks to flamethrowers to Street Fighter style martial arts, you won't be wanting for ways to lay down the pain. Not to mention that it's always more fun dropping a concrete donkey on a bigger group than a smaller one, of course. A standout in the turn-based artillery combat genre.
21. Ultima Underworld: The Stygian Abyss (Blue Sky Productions, 1992)
A game that was built from the ground up to not just be a more realistic kind of puzzle-driven dungeon crawler, but a full blown life simulation too. To that end, you had skills not just oriented around combat and spellcasting, but for swimming, conversing, identifying items and bartering with NPCs among many others. It had a lighting system and rudimentary physics for platforming, letting objects bounce off of walls (and activate switches) and no single set solution for most puzzles, letting the player take an innovative approach to figuring out the game's mysteries. Downright mind-blowing stuff for 1992, and the influence it's had on the industry since is immeasurable, inspiring games like Elder Scrolls, Half-Life 2, Deus Ex, and numerous others. It's a bit clumsy and awkwardly slow to play today, but it's nevertheless a great game and an important building block for gaming as a whole.