Your forgetting that the AI in Ratchet and Clank is incredibly simplistic
lol.
and that there normally werent massive firefights between different races of enemies.
Every single one of the Ranger battles? The Aquatos mission where you have the flame-forgeters against the Amoeboids? I could have sworn that that there's multiple factions in at least one of the Qwark Vid-Comics.
As for challenge. Halo has difficulty settings that make the game MUCH harder whereas Ratchet & Clank doesn't.
Which is 150% better than difficulty levels. It's fine-tuned to ensure a very specific progression of skill and players will constantly be pushed towards mastering the game, which is why many other kids games don't offer difficulty levels. R&C3 has various skill-based minigames (the Hacker, Vid-Comics, skills points etc), whereas Halo 2 kind of has achievements but mostly is just a shorter, much more linear campaign.
If you know how to play ratchet and clank already then you can easily get through the games without a problem.
That's the point. Then you play Challenge Mode where they ramp up the difficulty but also introduce new rewards for the risk. Furthermore, Halo 2's difficulty is static once you choose, whereas Ratchet & Clank's has levels that go up/down depending on how you're progressing through the levels.
Don't forget your also comparing 2 entirely different types of games as well. I don't think either of them are particularly better since they are both different genres and depend entirely on your taste.
Firstly, that argument is always an irrelevant one whenever it's used; you can compare anything so long as they have similar features. Secondly; both games are shooters. Ratchet & Clank 3 was marketed as a platformer so that they would stand out because there were so many shooters being made, and yet there weren't a lot of good platformers. The fact remains that R&C3, with their Battlefields and the reduction of platforming puzzles became a shooter.
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