Metal Slug Anthology
Long story short: I bought Metal Slug Anthology because the box says it's 4 player. It isn't. True to form, the included Metal Slug games are for one or two players, no more. Caveat emptor.
Metal Slug Anthology is a 10th-anniversary collection of the seven most important games in SNK's Metal Slug series, including the never-before-purchasable Metal Slug 6. The collection also includes some underwhelming unlockables, namely image galleries, sound test music, and a text transcript of an interview with Metal Slug staff members that is basically impossible to read.
The arcade games, fortunately, are implemented (emulated?) with 100% faithfulness to the originals. Single- and two-player shooting action has few examples as prime as the Metal Slug series, and they're all here. There is not a ton of variation between the different games, but it's a lot of Metal Slugging nonetheless (and with infinite continues, there's nothing between you and raw shoot-em-up action).
For the Wii, the Anthology engineers made up a treasure trove of control schemes. In fact, so many that one suspects they were mostly an experiment. I haven't tried very many of them myself, but at least the default control setting is fairly easy to use; and many of them don't require a nunchuk, so they're very accessible.
If you're a fan of Metal Slug and/or the shmup genre, this is a collection you shouldn't go without. Plus it's great for two-player co-op. But bear in mind that the "4" on the back of the box is a typo - this is no party game.
Progress: Gave Up -- Beat Metal Slugs 1 and 2