i was going to post a joke about sex with aliens but everyone already said the same thing.
man i really wonder this too, why is it that sci-fi seems to assume that alien life would be like humans with slight differences (or even worse HUMANS PLUS ANOTHER EARTH CREATURE EQUALS ALIENS wouldn't that be way too much of an evolution coincidence??)
i remember alot of my favourite star trek episodes were to do with really strange aliens (like huge space jellyfish - and jellyfish is just an approximation) or stuff like temporal loops and huge areas of space with weird properties. i always liked it when star trek done stuff that was legitimately weird! i also liked the episodes where a member of the crew would fall in love with an alien who's entire society is a metaphor for a tiny part of ours, too, though. for different reasons.
i don't even see avatar as a science fiction film, though. it's just a big dumb movie and the structure of it will be closer to indiana jones and the return of the pyramids than MY science fiction.
there are things to look at if you like to watch and hear a bunch of Cool Geeks hypothesize (fantasize) about what REALLY weird aliens MIGHT look like. i watched a thing on google video a while ago called 'alien planet' which is a mockumentary film where two robot probes go to an alien planet named Darwin IV and send back to Earth some....
'Astonishing Pictures' -
Johnny C. 'for Cox' McGinley.. there were strange aliens on that thing so check it out if that's what you want to see.
i would like to see a science fiction show have a prominent alien race that isn't humanoid or even really comparable to humans. it would take some thinking about i guess! more work than making a savage jungle people race.