Great idea for a thread but boy is it a hard choice!
1.Rome total war (the whole series as well but this was by far my favorite for sheer replayability, the graphics being great for its time and for me being the most interesting period of history. I can only dream they make a second (after Shogun 2 of course)
2.Command and Conquer Generals (By far my favorite of the C&C series, it was simply brilliant. Could have such epic battles in it. Graphics were great for it's time and was so addictive. Followed by Red Alert 2 and 1 but this one was just awesome. Like Rome, I can only dream they make a second but it's more unlikely than rome having a second)
3. GTA IV (again the whole series as well but I thought this was the best. The graphics were great, the story was great and the DLC too just makes it brilliant)
4. Age of Empires 2 (By far the best Age of empires ever made. I have spent on unbelieveable number of hours playing this game and still do now. Have had some great battles with my brother too. brilliant game.)
5. The FM series (has to be here, otherwise I may be killed! I would hate to find out how many hours have been used up playing these games, in particular FM2010. Can't wait for FM11).
Jesus that was a hard decision. Battlefield 2 could be swapped in with FM series. In fact yes I replace the FM series with Battlefield 2. Please don't kick me off the site plz

Battlefield 2 was such a great game, I think the best fps online (better than cod by a mile). So many hours spent playing with friends. Top notch game. Some other great games that can't make the list are the FIFA series, Team Fortress 2, Red dead Redemption, Smash Court Tennis Pro tournament 2, Pokemon Red, Blue and Yellow (the new can never be as good as thos games back in the good old days), the list goes on.