Developer Gearbox supported its breakout hit "Borderlands" with four memorable downloadable add-ons.

Sometimes, it takes a while before a game’s greatness becomes apparent.

When I first played “Borderlands” shortly after its release in October 2009, I didn’t get it. I fired the game up and played a bit solo, and it seemed boring. Though its cool, cel-shaded art style looked wonderful, its non-player characters seemed one-dimensional and its quests came off as minimalist and boring, all more or less riffs on “Go here. Shoot guys. Come back.” What’s more, the four distinct character classes all played similarly in the early going, until you reached level 5 and started to unlock their special abilities.

A handful of my friends picked the game up expecting it’d be the next game we’d play as a foursome. Two of them, a married couple, immediately returned the game once they discovered its split-screen mode was offline only.

But one of my friends stuck with it. Soon, he was raving to me about how much fun he was having, and the two of us started blazing our way through “Borderlands'” campaign. I still haven’t played “Borderlands” enough to max out even one character, but in a year marked by excellent “Halo” and “Call of Duty” games, it’s the multiplayer shooter I’ve found myself coming back to the most. Eventually, my friend and I found a couple of other players to plow through the downloadable content with us. We’ve finished “The Zombie Island of Dr. Ned” and “Mad Moxxi’s Underdome Riot,” and are nearly through “The Secret Armory of General Knoxx.”

If you haven’t payed much attention to “Borderlands,” it’s a first-person shooter set on a world called Pandora. Its paper-thin plot has a group of up to four adventurers searching for a mythical pile of powerful loot known as the Vault. In terms of design, Pandora reminded me a lot of a futuristic version of “Fallout’s” Wasteland crossed with “Mad Max.” It’s a barren desert filled with stray outposts and murderous bandits.

When you’re playing with a group, “Borderlands'” thin plot and simple missions are less nettlesome. The non-player characters who give you quests are often hilarious, as are the audio recordings you collect for various missions. Thanks to randomly generated stats, there’s an effectively infinite number of guns players can collect, which makes sorting through copious amounts of loot with your buddies and figuring out which weapons are best-suited to which characters its own fun, nerdy metagame. As you add additional players to the group, the enemies in Pandora grow stronger, requiring some cooperation to defeat.

All in all, “Borderlands” adds up to a great co-op game. I wouldn’t recommend playing it solo, unless you’re a player who really gets into “Diablo”-style stat boosting and loot collecting.