It would definitely help to know the machines in your collection already.

The more unique and challenging game is Creature. The easier and more standard game is AFM.

AFM while maybe technically deeper, is also much much easier. Pound on the middle, over and over again. Start multiball with an easy return shot, over and over and over again, and eventually everything will be ready for RTU (if not, start MB a time or two more and it will be...same shot that returns to the flipper). Standard MB where you complete the shots and there's a moving SJP. Then you continue to beat on the middle over and over again to Attack Mars. It has killer sound effects and voices, great humor, and is a very enjoyable game. But because of the repetition and return shots, it got stale really fast in my collection. (I also owned MM for 9 years, prior, which didn't help). I would get to RTU almost every session I played, and more often than not, you RTU when you get there. The roving shot on SJP, and the 5-way combo are about the biggest challenges it offers.

CFTBL is much more a sure shot oriented game. You have to hit the right shots at the right time, or nothing really happens for you score wise. You can't just beat on it until Multiballs rain from the sky. And the multi is a 2-ball only, very challenging. The Creature is in the different spot every time, and while Rescue and JP are easy enough, the SJP is difficult as is the maximum multiplier with the left ramp Swamp shots. Achieving 5x SJP is more difficult than any achievement in AFM. The art is gorgeous, fun 50's music, which rotates every day to keep from getting too stale, and a layered theme which is just perfectly integrated.

Again, it really depends on your collection. If you do not have any of the standard fan layouts, then AFM will be a lot of fun for you and your friends. It's not nearly as frustrating as Creature. If you aren't hitting your shots, then Creature will just spit you out dry....while AFM will still let you destroy a couple saucers and probably still start a MB or two. If you already have SM, MET, MB, MM, etc...any of those, then I'd go with Creature (and save $$).

Good luck!