To elaborate more on why I'm arguing against Size Matters, it feels as though nothing about it IS a ratchet and clank game, besides there being Ratchet and Clank and some creative weapons. I think it was Sanzaru that developed that game, though I can't be sure, and game series like R&C promptly tumble and faceplant when they go to different developers (i.e. pretty much every Spyro game after Year of the Dragon). If you insist on getting an R&C game for the PSP, you should settle for Secret Agent Clank. It's better than Size Matters in many ways, and it's pretty much the closest that outside companies have gotten to creating a game that really feels Ratchet & Clank. They also add a passable level of stealth gameplay into it, too.

I didn't play any Ratchet and Clank games so this is totally coming from a place of ignorance but wasn't it just a pretty standard platformer in a generation of nearly identical platformers (Spyro, Jak & Daxter, Sly Cooper, etc.)?

What was unique or good about Rachet and Clank that makes Size Matters not a Rachet and Clank game?

That's a debatable point. I've played both & while Secret Agent Clank isn't nearly as good, they're both fairly decent. I admit, Size Matters harkens a bit more to the original R&C, and not the sequels (limited number of hits you can take, and can't build up nanotech).

And frankly, I think you're doing yourself a diservice by avoiding outsourced games. Practically every good games for the PSP is outsourced, but not horribly, as at least with the GOW games, Santa Monica Studios was in talks with Ready at Dawn (the company that handled the Daxter game & the aforementioned GOW ones).

Also, High Impact Games, the company that made the title, has former members of Insomniac games on staff. Ready at Dawn, has former Naughty Dog & Blizzard employees.

Fat Princess: Fistful of Cake is a rather good game. Mostly "action with a side of strategy" game. I find it good for quick bouts. Controls are really good.

Monster Hunter if you want a bit more in depth game. I think there's a few different titles of it on PSP. I've played MH: Freedom Unite and attest for it.

Patapon (1 or 2) if you like rhythm games and have headphones (or not, if you want to get revenge on annoying relatives)

As the obligatory PSX game, Brave Fencer Musashi is reminiscent of The Legend of Zelda series, only not by Nintendo (orly?).

If you have a homebrew and like/have minecraft on the PC, you could give Lamecraft a look.

As far as I know, none of these listed have homophobic content. Although, it's been over a decade since I played Brave Fencer; I may not remember, sorry.