The '90s heyday of the real-time strategy game is long over, but Westwood Studios' classic Command & Conquer games are being kept very much alive.
CnCNet is a hugely impressive community project providing a network of servers for the C&C games, several of which were released as freeware some years ago. The website provides downloads of the games which are optimised for modern systems and ready for online play on CnCNet servers.
While I came to Half-Life late, Valve's 1998 masterpiece was the game that cemented my enthusiasm for games generally, and first-person shooters specifically. Replaying it almost 20 years on from its release, one aspect shines more than any other: the game's unique environments and crucial sense of place.
During the early history of the FPS, developers did not tend to prioritise settings. In classics of the form like Doom (1993), Hexen (1994) and Duke Nukem 3D (1996), settings and locations were only nominal, with little to no coherence between levels or episodes. Things began to change with id Software's Quake II (1997), in which the player progressed through numerous areas of an enemy planet, Stroggos. It was Valve and Half-Life, however, which gave the FPS its first - and perhaps best - coherent sense of place.
Return to Castle Wolfenstein could be called one of the most unheralded first-person shooters of its time. Developed by Gray Matter under the supervision of id Software, the game was released in November 2001 to excellent reviews - but it was ultimately overshadowed by both Medal of Honor: Allied Assault (released just two months later) and its own multiplayer spinoff, Enemy Territory.
Return to Castle Wolfenstein was both a resurrection of id's iconic Wolfenstein 3D (1992), and a thoroughly modern first-person shooter. Remarkably, the developers succeeded in both paying tribute to the "grandfather of first-person shooters" and fully absorbing the lessons from the games that followed in its wake. As a result, RTCW captures the thrill of both old school and modern shooters, and retains tremendous appeal over 15 years later.
Roughly every couple of years for about the last decade, I've returned to Diablo II. Blizzard's action role-playing game was released in 2000, and has been imitated many times but never matched. It's easy to see why so many developers have sought to make games that use the Diablo II formula: it is an addictive style of gameplay which is easy to pick up but hard to master; it can be adapted to different settings and game engines; and Diablo II itself was a tremendous commercial success.
There are also a number of reasons why Blizzard's game has remained the gold standard for action RPGs after all these years. The developer's famed quality control is one reason, as is their continued support (the game has been patched as recently as March 2016). For me, though, the single biggest asset the game has is its thrilling sense of challenge and difficulty: particularly in hardcore mode.