If you want an extremly fun shooter thats comparable to halo, get Time Spliters:Future Perfect. It has a creative and enjoyable story line(both single and co-op), more guns than you will ever need, tons of unlockable characters, a mapmaker, decent graphics, and a dash of comedy. Mix it all together and it makes for a pretty awsome game. but the best part is it works the best on GC because of the 4 controler slots which makes for the coolest splitscreen battles ever!
It is not considered a kiddy game because it is rated M for blood, violence and gore. But its actually not that bad, the violence is just kinda there. They dont shove it down your throat if you know what i mean!(god of war comes to mind)
Over all its a greatgame but not very well known so it didnt do as well as it should have. You wont be able to put it down once you start playing, so get it!