Developing a game is not easy. Especially it's harder to develop a game which will be a classic. But I think the hardest thing is making a serie of that game. Some games are very successful about this. Here are the best video game series since 2005;
Bioshock
I remember my first experience in Bioshock. Game started with an intro and then I took the control. But I was shocked when I realized that it wasn't an intro. I was in the game and that was in-game graphics. BioShock is absolutely a classic with its atmosphere, story and characters. Actually you can accept BioShock as a soul mate of System Shock. I can't wait for BioShock Infinite.
Dead Space
