OK, what do you like, what is your budget, and have you done any of them before?
The first one I would drop off is Disney California Adventure, while it is a much better park since the upgrades in the last couple of years, if I had to pick one park at the Resort would be Disneyland.
Knott's Berry Farm is America's First Theme Park, a lot less expensive than Disneyland, smaller crowds, and you can buy a Fast Lane Pass to avoid long lines on the major rides. Also has more and better Roller Coasters than Disneyland, if that is important to you.
Disneyland is the "classic" park, and has been popular ever since it opened on July 18th, 1955. A lot of variety, rides, attractions and great evening entertainment on many nights, such as Fantasmic! and Fireworks. That would be my first choice, but it does have the "crowd" issue.
So I would look at Disneyland Park and Knott's, and decide if the crowd factor is important to you...