What do you mean by "some games"? Do you plan on having games actually installed on it, or what?
For pure file space, WD Caviar Greens are the biggest bang for your buck, but the reason is because they aren't fast. Plenty fast to serve up media, but if you are playing any games that store their files on it or worse, have an OS installed on it, you'll definitely feel the difference.
If installing an OS or games on it, you'll definitely want something faster, Caviar Blue, or preferably Caviar Black.
Beyond that, the most important thing you can do is keep it nice and defragmented. To that end I recommend MyDefrag. Auslogics is great and zippy, but for large amounts of files, MyDefrag wins for it's strong ability to consolidate free space in one big chunk.