I played up to midway through 3 back on Xbox when they all first came out. Now I was able to get 2 for free, paid $1.49 or so for the first and replayed them... and wanted to finish 3. But hey, the trilogy is cheaper than buying 3 alone so huzzah! Seriously, for that price you get 3 games that will last you at *least* 50 hours if you run through already knowing what you're doing. Easily 120+ hours otherwise.
Also, CDKeys has yet to disappoint with delivery. Always get an email with the [working] code within one minute. Love this place!