Inspired by the "drawbacks to PC gaming" thread, obviously.
I'll start.
Games are almost always cheaper than the console versions of the same games.
You are offered freedom and flexibility in your hardware choices. You can keep the costs down and still play the game at a decent level of graphics and performance (read: better than on current gen consoles), or you can spend way too much money and get an incredible level of detail.
You are able to change graphical settings based on personal preferences. On consoles, if a game is set to run at 30 fps at most, that's all you'll ever get. On PC, you can change the settings to let the game run at a higher framerate, if you think this is more important than having extra flashy explosions, for example. In console games, the developers decide for you whether performance or graphical detail is most important, and you can't do anything to change it.
There is a huge amount of retro games available for you, if you are the kind of person who enjoys this. Especially if you went for the "reasonably priced computer" route, the software library for Windows PCs is very big.
You get access to a very comprehensible digital store by the name of Steam.
Practically all games support mice, which in many games offer a very high level of precision. In games where it makes sense, gamepads are also often supported.