OIC. Yeah, that's true. More action/adventure.
The fantasty/magical aspect of the items that Indy is searching for (the Holy Grail and that magic rock) don't make up for it?
I think that's an implication of an adventure movie. I guess you could tag it with fantasy, but I don't see science fiction.
There's no attempt to explain anything in the first 3 Indy movies "scientifically." Even Star Wars, which has much more of a "fantasy" blueprint than a sci-fi one has some sci-fi elements. I'd allow Indy 4 as Sci-Fi though.
Doesn't the fact that in Indy 3 they survive that fall in the inflatable raft and they jump the gap in the railroad tracks and land on the other side with no problem "Science Fiction" in it's most pure form?

1. Return Of The Jedi
2. Star Trek III: The Search for Spock
3. Star Trek (2009)
4. Alien 3
5. Total Recall
6. Star Wars: The Phantom Menace
7. Star Trek: Nemesis
8. X-Men Origins: Wolverine
9. Iron Man
10. Indiana Jones and the Last Crusade (albiet this time a woman)
Of course, since I haven't seen Wolverine, I'm assuming that that's definately science fiction and not just fantasy/adventure. (No offense, Tripe) Mutants are born, not made.