I'm also in Southern California, so I have a local bias. Another bias is that I don't care about celebrity photo-ops or signings. Harrison Ford signed my napkin for free; that's the most I'll pay for a celebrity signature.
I won't wait in a long line to get into a celebrity panel or to get special merchandise. I'm not a collector.
I'm a cosplayer and that's my main focus. I will say that the celebrities appearing at a Con can have a significant impact on the cosplay scene; I was at one Con where a Stranger Things star was appearing and there was a massive amount of ST cosplaying.
Here are Cons I've been to with my mini-reviews:
Emerald City CC: A favourite. Very well-run. The big celebrities were in the main room so everyone could see them! How brilliant is that? And huge TV screens were all over so that you could see them anywhere you were.
FanX Salt Lake City: Loved it. Some amazing intense cosplay. I attended the first post-Covid FanX and in spite of the hiatus it was well-run. Super convenient, I stayed at a hotel literally across the street. There were two breweries within easy walking distance (I'm a craft-beer person).
Phoenix Fan Fusion: One of my favourites. It's no longer held in the middle of summer! Now it's Memorial Day Weekend. (Should be in winter, no?) Yes I was there waiting outside in 114f temps and the soles melted off my shoes, but once inside they have the AC cranked up to Winterfell.
Los Angeles Anime Expo: My longest-running event, been going over a dozen years due to my Anime-fan daughter. (She introduced me to cosplay.) This has the best cosplay of any Con I've attended, though of course largely Anime. It's by far the worst-run event. Every year it feels like the people in charge have never done a Con before. At some point they said "Hey, let's mail out the badges like the well-run Cons do!" but then they made everybody, badges or not, wait in the same super long 6-hour line. On the plus side they have an unusually lenient prop weapons policy.
WonderCon: I'm biased; I work across the street at Disneyland, and I love just being able to walk to a Con. It has a big outdoor area with fountains and steps giving the best huge group-photo place I've seen.
Star Wars Celebration: Also just across the street this year! I was amazed how much LESS Star Wars merchandise there was, compared to a normal Con. This event is run by Disney so it's just booths displaying things available, or soon to be available, in the Disney parks, and booths displaying costumes from upcoming Disney films and TV programmes. I couldn't find a single booth selling lightsabres, or Jedi robes, or anything else related to Star Wars. Please Disney let in outside people selling Star Wars related things!
San Digo Comic Con: Very well run; no lines to get in, they just open all the doors and in you go. In spite of being in Southern California this was my first year attending. I know it's the first post-Covid SDCC and I should cut it some slack, but I was underwhelmed. It was pretty much like the other Cons, but harder to get to and much less cosplay. All in all one of my least favourite Cons. A cool feature is the way that a local street lined with restaurants and pubs T-bones into the Convention Centre, all closed to vehicular traffic, creating a huge street party vibe.
Monsterpalooza: A very special Con! It has a unique vibe, being a sort of Con but also a film industry Trade Show, full of firms who do makeup, prosthetics, props, etc for the film industry displaying their wares and doing all-day makeup demonstrations.
Los Angeles Comic Con (AKA Comikaze) A nice largish Con with plenty of cosplay, very well run. It used to be Halloween weekend but it's in December this year.
Long Beach Comic Con and Long Beach Comic Expo: smaller events, good if you don't want big crowds and long lines. It has a good place for people with TV/film cars to display them.