In my review of “Bastion” on Wednesday, I talked a bit about the idea that Microsoft’s Summer of Arcade program may be starting to outlive its usefulness.

Back when Summer of Arcade launched in 2008, Xbox Live Arcade was a growing platform. We’d long since graduated from the days of 2006, when the marketplace was dominated by classic arcade games like “Time Pilot” and we couldn’t even count on a new game every week. But there were plenty of weeks with releases people have long since forgotten about. Are you still playing “Bliss Island,” “Rocky & Bullwinkle” and “MLB Stickball?” Didn’t think so.

While these kinds of low-profile, low-praise games still get released on Xbox Live Arcade with regularity, we now often see multiple titles released each week. Additionally, the number of terrific games has risen to the point where we can probably expect three different Microsoft-backed showcases this year. Last year, after all, brought us the annual Summer of Arcade, but also House Party and Games for the Holidays. (Conveniently, all these promotions tend to fall when retail releases have slowed to a trickle.)  Summer of Arcade follows a spring Block Party and will almost certainly be followed by another Games for the Holidays-type promotion.

But there are plenty of great games to be found outside these promotions, making the decisions about what games get included in the promotions seem random or arbitrary. “Bastion” and “Fruit Ninja Kinect” have little in common beyond the fact that you can’t find them on PlayStation 3.

In light of that, here are a few downloadable games I’ve been enjoying over the past few months. Not all of them are exclusive to the Xbox 360, but they all hold their own against the Summer of Arcade and Block Party titles and shouldn’t be overlooked.

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“Trenched” (rated T, $15 for Xbox 360): The latest game from Sonoma native Tim Schafer and Double Fine Productions is a blend of frenetic mech shooter and strategic tower defense. You pilot your “trench,” essentially a World War I-era foxhole mounted on a chassis and a pair of giant robot legs, with guns. (It’s as delightfully goofy-looking as it sounds.) As you run around and shoot enemy Monovisions, fantastical creatures made in part from cathode-ray TVs, you gain scrap used to build turrets, repair stations and other helpful emplacements.

Before each stage, you’ll customize your trench’s chassis, legs, weaponry and emplacements in an effort to find the optimal arsenal. At the conclusion, you’ll be awarded a medal based on your performance. When played cooperatively with up to four people online, outfitting everyone’s trenches and planning out a core strategy turns into a fun, prematch metagame.

In addition to being a lot of fun to play, “Trenched” is also a feast for the senses. The Monovisions, in particular, look fantastic, and the sound design gives every weapon a distinct ratatattat or appropriate thump. I’ve yet to play another downloadable game with such aurally satisfying gunplay. Double Fine’s reputation as merchants of mirth is in evidence, as well, particularly in the descriptions of “Trenched’s” various upgrades and customization. (Of the Jungle Camo Paintjob, the game says, “It doesn’t really work on the Monovisions, but at least it keeps the snakes away!”)

My friends and I sunk a good six to 10 hours into “Trenched” so far and are hungry for some more downloadable content.

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“Outland” (rated E10+, $10 for Xbox 360 and PS3): This side-scrolling platform-jumping game from Housemarque (“Dead Nation,” “Super Stardust HD”) has been out on the Xbox 360 since late April, but its PS3 release was delayed until last month because of the PSN failure.

“Outland” combines some “Metroid”-style exploration and platform-jumping with some “Ikaruga”-style polarity switching. A tap of a bumper button switches the character from blue, which is immune to blue projectiles and capable of jumping onto blue platforms, to red, which functions similarly. Additionally, the main character can only damage blue enemies when he’s red and vice versa. It takes a little effort to get the hang of, and I’m definitely much more tentative a player than whoever’s destroying everything in sight in the above trailer, but the game is a fluid, satisfying platformer with a gorgeous art style, to boot. Additionally, it includes a two-player co-op mode that I haven’t had a chance to try out yet.

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“Magic: The Gathering – Duels of the Planeswalkers 2012” (rated T, $10 for PC, Xbox 360 and PS3): Why this is called “2012” when the game came out this spring is beyond me, but the latest iteration of “Planeswalkers” offers some enhancements over the first “DotP” [review] while bringing back some elements I found frustrating.

If you’ve played the Magic: The Gathering collectible card game, you have an idea how “Magic 2012” works. You have a deck made up of creatures, spells and mana-generating lands. (Mana is used to summon creatures and cast spells.) You’ll use those cards to either reduce your opponent’s life from to zero or to make him run out of cards.

“Magic 2012” features a much more robust single-player campaign than the original. There’s a core campaign, in which you defeat computer-controlled opponents to unlock all the game’s different decks of cards. Then there are challenges, which require you to defeat a powerful opponent in one turn using the cards you have in hand. New for “Magic 2012” is Archenemy Mode, which has three human or computer-controlled players teaming up to tackle one overpowered, computer-controlled boss. This new mode is a great addition for people who prefer online co-op to the typical one-on-one meatgrinder.

While “Magic 2012” includes a collection of creative decks, with more customization options than the first “Planeswalkers,” it’s frustrating that the sequel doesn’t allow players of the old game to import decks from that game for use in “Magic 2012.” Backward compatibility would’ve been a small thing to include, and it would give the competitive online matches some additional depth.

Additionally, developer Stainless Games brought back a feature that allows you to see what decks your opponents are using in online matches. This is great in Archenemy Mode but can be frustrating in one-on-one play if you get one of those opponents who will change decks after seeing yours in the hopes of getting a favorable matchup. The feature was taken out of the first “Planeswalkers” after the community of players complained about it, so it’s puzzling to see it return here.

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“Ms. ‘Splosion Man” (rated T, $10 for Xbox 360): This game from Twisted Pixel is a sequel to a game that was part of the 2009 Summer of Arcade lineup. While I bought this game last week when it launched, it reminded me that the original “‘Splosion Man” was sitting on my Xbox 360’s hard drive, unplayed. So instead of firing up “Ms ‘Splosion Man,” I decided to start with the original.

The gameplay is simple. Both ‘Splosion Man and Ms. ‘Splosion Man can explode with the press of the button, a move that serves to vault them into the air and destroy any surrounding material or enemies. Essentially, the two games play like a blend of platform-jumping and puzzle-solving, as you string together your explosions to traverse the levels. I’m enjoying “‘Splosion Man” tremendously and have full faith that the sequel can stand proud with this summer’s best downloadable games.

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