I played through Tony Hawk's Underground 1 and 2 on the original Xbox, so here's some words:
This game follows you and Eric Sparrow, two friends who skateboard from Jersey, as you both try to go pro. There's some plot twists and turns where Eric betrays you, but overall the plot definitely just exists to get you from level to level and to naturally unlock parts of levels as you progress. It's a good system! The cutscenes have some funny dialogue, really good animations, and pretty good voice acting that makes watching them a pleasant experience.
Very nice graphics for the time, runs at 720p on the OG Xbox which looks pretty good! Almost always a solid 60fps except when there's particle effects taking up most of the screen.
Controls pretty well, althought wallplanting is significantly harder to do in-the-moment than sticker slaps from THUG 2, so I found myself failing some combos due to hitting a wall.
I really enjoyed the story, though the last mission where you have to ride Eric's line is disproportionately harder than all the other missions before it. But I definitely felt compelled to actually complete the story.
The locations, while they mostly felt same-y, were all great, pretty large, and had plenty of secrets to find. Looks like each level has at least a secret tape, and possibly an unlock for a retro level from previous games (though I'm bad at video game and only found 1)
One oddity is that there's a pretty decent amount of "driving" you have to do in the story. I found it a little clunky for a game about skateboarding, but it's limited to like one forced segment per level, so it's not annoying.