Sometimes a game is great, sometimes it's not, and then we have the sequals, sometimes a sequal comes along and either makes a bad game good, a great game even better, or cahnges little, thses are the sequals that took everything about the origioanl and improved it.
Honerable mentions: Dawn of war 2, super mario world, metal gear solid 4, god of war 3, the sims 3
10. Tomb raider legend: Take a great game and completely re-vamp teh visuals, vioce acting, story and gameplay to the point that it barely resembels the origonal fraonchise, was the concept behind this sequal/reboot, and it gave us probably the best tomb raider game ever.
9.Super mariogalxy 2:take a great platformer and improve EVERYTHING and you've got not only a great sequal, but one of the best platformers ever
8. Civilization 5:they improved the graphics and made it even more acessable than the last game, and it's just as fun as any other civ game
7. Doom 3: though the gameplay didn't cahnge, the graphics and scares ceartinly did,a nd it was as much fun as the origional
6. Supream commander 2: sliker graphics, better frame-rate, larger scale, everything was better in this sequal
5. Red alert 2: An amazing RTS is made better with new units, story, graphics, and mission variety.
4. Left 4 dead 2: now truethfuly my computer can run this game (well) but even with a low framerate i could tell that this was WAY better than the first one, more sepcial infectied, improved graphics, more weapons, funnier dialog, if the gameplay had been improved, this would be even higher (i'm not saying the gameplay is bad, it's just EXACTLY the same as the first one)
3. Uncharted 2:take one of the bestaction/platformers ever and make it betterin every way and you've not only got a great sequal, but one of the best games of all time
2. Starcraft 2: The first starcraft was a phemonenon, and still is to this day, but starcraft 2 is far superior to it's predacesor, great graphics, varied missions, an involved story, new units, improved battle.netthe only thing keeping this from number one is no zerg or protoscampaign (though the terren campaign is just as satifying)
1. Half life 2: the first half life was a good game (though it has aged) but half-life 2 took everything that was amazing about thalf life and improved upon it ten-fold and is infinately better, resulting in one of the greatest shooters ever.