Video games are always meant to be fun. Although it is a joy to play alone, the fun quotient radically increases when you go about a mission with a friend by your side. Yes. We are talking about Co-op games and the immense enjoyment it has provided to gamers over the years. So which are the top co-op games of all time?

Here is a list of five best co-op games of all time.

Diablo 2: "Diablo 2" is one of those games which you will enjoy regardless of the fact if you are playing alone or with a friend. However, most will agree that the game became a legendary experience as soon as it was played in co-op. Developers Blizzard took this opportunity to increase the difficulty level of the game a bit every time you got a friend moving in with you, and this made the game even more addictive and challenging.

You could start a campaign with as many as eight heroes (representing your friends) at a time. This means that you start the MMO with an advantage of eight powerful companions with their own special abilities.

Gears of War 2: "GOW 2" actually deserves appreciation from all the co-op fans all over the planet for making drop-in/drop-out co-op the standard for cooperative gaming today. This game was all teamwork with merciless killing and ground-breaking scenes for hours and hours.

The new "GOW" couldn't really match up with its predecessor.

Rock Band 3: "RB3," according to many, was the ultimate party game that united four people together to form the ultimate rock band of all time. With a ridiculously large library of pre-installed songs, this game actually brought everybody together. More songs could be added via DLCs. The Career mode is more interesting and helps you bond with your friends even more with everybody getting their fair bit of spotlight and recognition.

Portal 2: This game is one of the most unique co-op titles of all. Two wacky robots, P-Body and Atlas, represent you in the game and make their way through a host of complex puzzles in Aperture Science's test chambers. The game actually forces both the players to cooperate to solve separate parts of a puzzle before coming together in the end to provide the finishing touches.

Halo 3: "Halo 3" is one of those games that are re-defined the meaning of co-op gaming over the years. Although the game has an impressive single player experience, the missions become more interesting when you are joined by another three players to aid you.

The most fun fact about the co-op mode of the game is that now vehicles get multiple seats and the difficulty levels are nearly a death wish if you go alone. This is where you need a friend to intervene and help you out from that awkward position.

(What are the games that you guys think should also make the list?)