Gears of War 2 is the sequel of Gears of War and in terms of the style of gaming, is slightly more forgiving to new and old players. The game has many more new additions to the old Gears including special Executions that will allow you to finish off a enemy with style. However some guns have specific executions that can only be done with that gun. Two guns with such executions are the Gnasher, and the Longshot. There is also a difference between the executions length you can choose from, like short, medium, and long. There is also a special Meat shield executions which you take your downed enemy and use them as a human shield, taking up bullets for you before they fall to the ground. However just taking them as a meat shield (with an exception of the leader in capture the leader) counts as killing them and even if you get headshot before a single bullet hits them and you die, that person won't get back up.
Gears of War 2 there are new enemies with only one special enemy that can be found three times in the first game removed. First there is the Kantus which is a healer, if one of the locust are down, the kantus will start screeching and revive them. However even after the locust is revived the kantus will continue to screech for a couple of seconds leaving it open for attack. Second there are Tickers which are, literally, walking bombs. They will attempt to run at you as blow up, in groups these little guys can kill you instantly. Thirdly there are Bloodmounts which are fierce melee opponents. Bloodmounts charge right at you and only stop if you shoot their helmet enough and have a rider who will shoot you unless you kill him.
Gears of War 2 also has a game mode that is all co-operative called Horde. You and four other friends hold out against fifty waves of locust ranging from the regular Drones to the new every enemy besides the berserker. This leaves you to waves of enemies where you only respond between waves. This can be challenging to new players if they haven't played the campaign and faced all the enemies.
Gears of war 2 also has new weapons, like a whole new Hammerburst and new heavy weapons which you can't carry everywhere, just till they run out of ammo or you drop it. You can't mantel over walls with heavy weapons ether so that restricts the places you can take them. Like the previous Gears there is plenty of ammo so running out of ammo isn't a concern.
Gears of war 2 also has a deep story which concerns the future in Gears of War 3. It also gives you information about the Locust Horde and some information about Sera's past, and some info on Jacinto the last human city in the game. I won't say much but I will say that a third group is introduced in the game. The Lambent, a army of locust corrupted by imulsion the planets fuel. It even gives you a first hand encounter with a locust Brumak turning into a lambent beast.
The game is very good but even now I have to say the third game would be the best selection instead of Gears of War 2, though the games good, the third game is probably a better selection to this game as it's more challenging that this game and has even more enemies.