Long answer: There are many others though, and FL and Acid don't really fall into the same category of software as Cubase, they're kind of their own thing.
- Pro Tools
- Logic Studio (obvious disadvantage: requires a Mac)
- Ardour (more limited, FOSS offering)
- FL Studio
- Ableton Live
- Renoise (this one can use VSTs, so you can get pretty nice production value with it considering it's still fundamentally a tracker)
Most game composers are gonna use something under the "Traditional" category since they generally offer robust mixing environments borrowing metaphors from traditional sound engineering. Like Chris said though, whichever one you use should be up to you and your tastes. The artist is more important than the tool. And the plugins are more important than the DAW. See if your local Guitar Center or Sam Ash will let you try out Cubase and Pro Tools on a demo workstation. Sonar, Ableton, and Reason should offer a trial version for download.
* If you want to get a solid DAW that supports everything the big-name ones support to learn on for free or use professionally on the cheap, Reaper has an infinite, uncrippled trial version, and a license is fairly cheap. It's a little different from the others in the Traditional category, but follows the same basic patterns. The other DAWs come with a lot more nice sounding virtual instruments and effects plugins (it's the reason I went for Logic, and the student edition of Logic Studio is only $150 woo!), but Reaper can stand on its own for the essentials (EQ, delay, basic reverb, compressors, etc.). It's routing interface is a little different and might feel strange to some, but it's very flexible.
Ardour is another alternative, but I've only ever gotten it to work stably on Linux distros. Not worth it yet IMO.
[EDIT] Forgot about Ableton. Ableton's built more for DJs and electronic musicians, but as such it sort of lends itself to being able to compose modular music, lets you easily prototype transitions to different music cues.