^ Gene Hackman hasn't made a film in years. He retired in 2004.
It is based on what people search for on IMDb, regardless if actors are dead or retired. Young Frankenstein is popular at the moment (always during the Halloween season) so I guess it has to do with that.
*edit* The currently ten most looked up (popular) movies at IMDb featuring Gene Hackman are
1. The Firm (1993)
2. Young Frankenstein (1974)
3. The Replacements (2000)
4. The French Connection (1971)
5. Superman (1978)
6. Unforgiven (1992)
7. The Royal Tenenbaums (2001)
8. The Birdcage (1996)
9. The Poseidon Adventure (1972)
10. Mississippi Burning (1988)