If you want to check out the latest Metroid game on Nintendo 3DS, I'd advise you to do it soon.
Metroid Prime: Federation Force isn't really what you think of when you think Metroid. Nintendo's adventure game series has always been about exploring a vast, abandoned labyrinth of a planet or a space station, fighting off lingering creatures while upgrading your arsenal so you can explore more and more of the world. Save for one best-forgotten attempt at competitive multiplayer, the games have always been solo experiences. Federation Force is dressed in the trappings of Metroid, but it's really an odd spinoff: A cooperative multiplayer first-person shooter, split up into brief, discrete 10-to-15-minute missions.
If you want to play through it alone, you can do so. But it's a sub-optimal experience, for a few different reasons. The best way to play Federation Force is with partners, either in the same room or online. Since the active userbase of mid-tier online shooters like this usually drops off significantly after launch (and since I didn't even see that many people playing it this week), I'd advise you to play soon before the rush is over.
I played Federation Force on the "New" model of Nintendo's portable console, which means I had what I consider an advantage: I could use the system's second analog stick to aim my shots, rather than have to rely on motion controls for aiming. After a brief adjustment period in which I got used to the idea of actually playing a twin-stick game on the 3DS form factor, I found this worked surprisingly well. It wasn't as comfortable as holding a home console controller, but neither was it the hand-cramping experience I dreaded.
The controls weren't awkward, but the rest of the game design can feel that way. Rather than one large world, Federation Force is broken up into a couple dozen disconnected missions. Jump in, blast some aliens of varying sizes, jump out, get graded on a three-star scale because that's how all videogames work now. Along the way, you can find hidden "mods" that let you upgrade your warrior over time, adding to your inventory space, powering up your weapons, etc. So there's some value in repeating missions since you can keep finding upgrades.
I decided at first that I'd like to simply solo the whole game. Why bother involving others? This wasn't a big deal as long as the game stayed balanced for a solo player, but things quickly went out of whack. The game's first boss fight, the seventh mission, features an instant-kill attack---if the boss swipes you, you're dead, you get booted out to the game's menu, and you have to repeat everything you just did. This is clearly built for a multiplayer scenario, in which players can revive each other. There's no concession to this discrepancy if you're soloing; you're just supposed to deal with it.
Federation Force doesn't really have a single-player mode, in other words: you're just playing multiplayer by yourself, and there are no tweaks in the gameplay structure to accommodate this. If you are playing by yourself and you want to quit playing, tough luck---if you try to exit the level, the game will punish you just as it would punish a player who ditched a multiplayer game, and destroy one of your hard-earned mods.
After realizing that a solo experience is highly undesirable, I decided to log in and see if I could group up with others. While there were very few players online, I was able to get into a couple of levels that I needed to complete alongside a partner or two. I'm not sure if Federation Force tweaks the difficulty of the levels based on how many players are playing, but it certainly doesn't seem like it does. A level that was brutally difficult with two players became bearable with three, and a boss fight that we couldn't scrape by as a duo became a total cakewalk with four. (Sadly, that was the one and only time I could get a full group together.) Not being able to use voice chat certainly didn't make things any easier (the game gives you a very small list of different things you can say to communicate, like "Follow me" or "Thanks").
Yes, it is quite a bit more fun to run down Federation Force's hallways and headshot its Space Pirates when you have a group. But a lot of that, it seems to me, is because the game is designed to be much easier when you have a team and very challenging, even inhospitable, to a solo player. Of course, it makes all the sense in the world that a multiplayer-focused game should be balanced that way. But do plan on trying it online, rather than attempt to use it as a substitute for a true solo Metroid.
And speaking of which: Hey Nintendo, it's been nine years since the last traditional Metroid Prime. Maybe we could have another one of those at some point? Just throwing that out there.
