I may be in the opposite spectrum here. I go to CGA more often since it's closer to where me and my family live. We never really go out of our way to go all the way to Vallejo and SFDK for some reason. I only went there twice: once when I was really little and before it was bought by Six Flags, and the last time which was in 2007 I believe, just when it was renamed Discovery Kingdom. I enjoyed it, but because I haven't visited it often as CGA, I can't really say or appreciate much about the SFDK or the way they use its theming.
Yes, I do think CGA has been in a bit of a rut between the 90s and 2010s, but like what everyone else has been saying, stuff like Gold Striker, Mass Effect, Railblazer, and the new events are really helping bring new life into this park. I kinda feel like they're trying to return some of its greatness (pun not intended) that was once lost from the Marriott days. I'm still excited to see these new developments coming in the future, most especially the hyper coaster and entertainment district. I feel like CF is really starting to take this park in the right direction, and I still wish them the best of luck.