I'm generally one to argue for XC2's merits when it comes up in discussion, but the game is certainly not without its faults, and I also really do love XC1, having just dropped 95 hours into DE to finish the collectopaedia, Colony 6, and the Superbosses.
Both games do certain things better than the other. XC1 has perhaps the best sense of world building I've seen in a JRPG, the Bionis and Mechonis is just such a cool concept, and the world design does a good job of reminding you of the kind of world you are living in. The game also starts with a bang that gets you hooked almost immediately and motivated to see what happens next. The game is fairly well paced throughout, with story beats building tension as it gets closer to the ending and things go nuts, but also gives you time to breathe and go do side quests. The game isn't perfect through (no game is), and the side quests almost always amount to "go collect x number of thing" or "kill x monster", and a lot of the times they have good storylines attached to them, but there's just so many with so much dialogue, that you end up mashing A instead of actually reading them most of the time. I also think a lot of the characters are cool conceptually, but often come across really awkwardly when they interact with one another. Like, why does everyone develop an interest in Shulk's love life in the middle of the game? Dunban, I get it, Sulk and your sister is your OTP, and Melia, don't you have other things to be worried about at this particular moment? And why is it any of your business, Sharla? And how many times does this exchange happen: Shulk sees a bad vision. "What is it?" says Reyn, clearly noticing Shulk is panicked. "It's...nothing" Shulk says. Bad thing starts happening. "Shulk man, You've got to TELL US when something is bothering you!" Reyn says. "Okay, I will from now on" Shulk says. And then he just never learns!
Having just restarted playing 2 after having finished 1, I do immediately notice a few differences, some due to being designed for better hardware, some artistic. While XC1 starts with action and mystery, XC2 has this kind of mixture of optimism and melancholy. It doesn't awe in the same way, but it does do a good job of characterizing Rex. The combat also feels a lot weightier and slower than XC1, but by the time I had blades and party members, I remembered why I really liked it. There's a lot to keep track of when building up combos, and pulling it off feels really satisfying. The animations and models are also noticeably better off the bat, even compared to DE. The nopon (who are huge in this game after having gotten used to XC1 again) have actually rendered faces instead of textures (Heropon Riki was done dirty). The animations are really nice too, especially in the action scenes. And yeah, some of the character designs for the blades range from eye brow raising to "what were they thinking?" I actually really like Pyra's concept art design, but the 3D modelers seemed to have exaggerated the hell out of her chest, and some of the optional blades are pretty yikes. Having said that, there's also some amazingly designed characters, which I guess is what happens when you have multiple guest artists involved.
When I first played XC2, I remember my thoughts were something like this. "I'm enjoying this game, it's really fun, but XC1 is a classic, and I don't think this can possibly top it." I remember think this right up to Chapter 7. But Chapter 7 is where XC2 really begins its march to the endgame, and its where I became enraptured with the story and characters in a way that even passed my experience with 1. The characters had all really began to grow on me, and here they just keep getting great moments. I just felt there was so much at stake, and not just for the heroes, but the villains (who are more complex then their XC1 counterparts, who range from "I did what I had to" to cacklingly evil). And everything from chapter 10 onwards is just ridiculously impactful. The game gets philosophical in a way the previous game hadn't, the backstory is given so much more depth and complexity, and the heavy emotional moments feel so heavy. The story climax hits me like a truck even 2 years later.
So while I think XC1 is the more consistent game, it just never reaches the highs for me that XC2 does in terms of combat, story, and characters, though it certainly has the trophy for world building. Both games are excellent and do things extremely well, but at the end of the day, XC2 just stands out to me more.