I would say Disneyland. California Adventure has roughly half the number of attractions that Disneyland does. True, California Adventures target audience is teens, but even with the recent Carsland addition it is still not a full day's park whereas Disneyland takes a full day or longer to experience everything, and that's on a relatively uncrowded day. Although, for just a little bit more you could buy a Park Hopper and enjoy the best at both parks for a day (hoping its an uncrowded day).
Want coasters? Disneyland has four (Space Mountain, Big Thunder Mountain, Matterhorn, and for the kids Gadget's Go Coaster). California Adventure has two (California Screamin, which is the only coaster in either park with a loop, and Goofy's Sky School).
Want a water flume? Disneyland has Splash Mountain with one of the biggest drops in Southern California, while California Adventure has Grizzly River Rapids.
Want shows? The parks are roughly even. Disneyland has Fantasmic! and Fireworks while California Adventure has the World of Color fountain show and Aladdin Musical Spectacular.
Interactive game rides? They're even. Disneyland has Buzz Lightyear Astro Blasters and California Adventure has Toy Story Midway Mania.
Dark rides? Disneyland wins with Haunted Mansion, Pirates, Small World, Snow White, Pinocchio, Mr Toad, Alice, Roger Rabbit, and Pooh. California Adventure has Ariel's Adventure and Monster's Inc.
Thrill rides? About even. Disneyland has Star Tours and Indiana Jones, and California Adventure has Tower of Terror, and maybe Soarin over California. perhaps Radiator Springs Racers as well.