The Dink Network

I know I writed subject really annoying, but really this is imporant for me. Since my grades were really bad a school, my faher banned me from playing computer for a very longtime. Now that I got that grades pretty well, I am again permited to play computer. But now that I played it I feel really bored with my games. Then I installed 3 other games at the same time(which are warcraft 3, prince of persia the two thrones, the movies.) afer that day my computer crashed so we formatted it(I don't know whats format on english sorry maybe it's same) now I don't have my old games too. I only installed Fallout New Vegas but since I finished that game with every ending I am still bored. Now what I want help at is. Which game should I buy. Bu they must be these games:

Dragon Age 2: A frýend told me first game was pretty good(I didn't played it)and I love RPG games. But I don't know one thing. Do I need to buy fýrst game before 2? That makes a dýffýrence?

Assasin's Creed: I didn't played this game too. But If I play thýs game I star from first game.

Star Craft 2: Yeah I didn't played first game. But that makes a difference I need to play that? I want to know that.

Last Note: I want full answers please. I mean(for example) not only buy SC2 explain me why to but that game why you enjoyed it. And at last don't say buy all of em, it's not an option for me. Thanks all... Phew it's hot here and I am tired of writing I am not used to this