action: either A) no plot but tons of killing and kewl explosions, one liners and some dude who only uses one gun that never reloads but can kill whole armies. doesnt matter if main chatacters backstory is nonexistant as long as they blow up a ton of shit with clearly fictitious weapons or 'realistic' and brutal with an engaging plot and a real asshole for a badguy who dies in some really imaginative way at the end.
action sci-fi: decent plot with characters that make sense. gritty-industrial-real sci-fi movies like alien are what i like. ****en star wars (the new ones) are an absolute shame to the genre. who the hell puts a stupid wierd alien who cant even talk properly in charge of a whole planet or whatever it was they did with jar-jars character. too much bullcrap and stupid aliens in starwars, plus very VERY gay robots.
thriller: well written and scripted with a twisting plot that isnt predictable or totally cliched... would only expect that in an action flick.
comedy: actually has to be funny.
horror: if i can tell who is going to die and who is going to live after the first 10 minutes... its a bad film.