Doom RPG takes the greatness of classic Doom, mixes it up with some RPG elements and makes it portable.
Doom RPG has a lot of levels for a cell phone game and will take you about 4-5hrs to complete which is pretty good compared to most games. I actually sat around at home in front of my computer playing this one as it had me hooked.
Once you finish the game you get given the cheat code and you can use that to get to a debug room which is kinda neat, you also have level select and can just goto whatever level you want to re-play.
All of your old time favorite Doom weapons have made it into the cell phone rendition along with the addition of a new one, the fire extinguisher. You have to get ammo for it but it allows you to put out fires spread around the base, earning you EXP. More of a novelty than anything else, but walking into fire does hurt you so it's worth putting it out if you have to get past or if you really want to level up like me :P
Doom RPG is a surprisingly fresh mobile title amongst the waves of platformers and is definitely worth checking out.