Today, almost every single video game released allows you to play against other human players online. There are a full notable exceptions, such as Dead Space and Fallout 3, but even traditionally single player franchises like Knights of the Old Republic are integrating or completely going multiplayer. In fact, Bioware recently announced a Knights of the Old Republic MMO (massively multiplayer online), so the next KotOR release won't have an ounce of single player gameplay. However, a shoddy online video game service can break the best of games. Some games like Company of Heroes, which received critical acclaim left and right, suffered because of poor online offerings.
The Right Service
As previously mentioned, Company of Heroes used Relic's own online video game service. Players would frequently crash, automatching was difficult, and lag was systematic. Compared to stable offerings from competitors like Blizzard (with their stable and fantastic Battle.net service), Relic's online video game service was weak and drove many gamers away from an otherwise fantastic game. Over time, the service grew more stable, but the shattered confidence of many gamers takes a long time to repair. Another example of this is Funcom's Age of Conan MMO, where the vast majority of players left after poor changes were made to the game against their approval.
On the plus side, there are some great online video game services available to gamers that can greatly increase the enjoyment they get out of games. Blizzard's Battle.net service is just one of many, although there are only a few games that can be played on there (such as WarCraft III, StarCraft, and Diablo II). Another great online video game service is Valve's Steam. Valve's the maker of Half-Life, Left 4 Dead, and they also developed Counter-strike Source, one of the most popular first person shooters ever. Gamers get access to a wealth of features that can't be found anywhere else atop a stable platform that very few people have problems with.
Even Wii video games, designed primarily as “party” games meant to be played split-screen, often have online functionality. Some notable titles include Super Smash Bros. Brawl and Mario Kart Wii. However, Wii gamers will many less options available to choose from when they want to play online. For online video game services, the Xbox 360 has the best built in one in the form of Xbox Live, and while the PS3 also has a decent one, consoles simply can't compete with such online video game services like Steam and Battle.net found on the PC.