An excellent choice! That should keep you entertained for weeks and weeks! Definitely worth it to go back and play through Half Life, Half Life 2, and Episodes 1 and 2 to get caught up with the series. Nobody does cinematic gameplay like Valve!
I must also voice support for The Witcher if you are an RPG fan, especially if you prefer story and atmosphere to looting, customization, and leveling up. (Though you do limited amounts of all of those things still). The game is a terrific start to the series and can draw you in with its great story and cinematic feel. It also takes an ironically refreshing approach to morality...instead of the good/evil choices present in most RPGs, your decisions have realistic ramifications. For example, you may be tempted to save someone's life, but this person may come back and kill others later on.
However, if you are into looting and character customization, then an MMORPG or Oblivion (especially if you mod the living daylights out of it!) may be more your style. There are still people out there playing Oblivion nearly two years after its release due to the number of mods and the sheer amount of content and expansions available in the first place.
Going back in time a couple of years, you might also check out Chronicles of Riddick: Escape from Butcher Bay. It is one of those games that doesn't have a TON of name recognition but is really well done and easily worthy of a play through at the prices you can find it for these days (under $10). Of course, going back this far in time, you may also consider Far Cry, which can also be found for under $10 and will tell you more or less if Crysis is worth the purchase, as they are very similar games.
Also, if you have any historical interest in World War II, the Brothers in Arms series might be worth checking out. The series is extremely thoroughly researched and historically accurate; they actually sent art teams to Normandy to sketch buildings that were encountered by the troops during the invasion and recreated them with a painstaking amount of detail.