they're very difficult to compare since i think their stories serve vastly different purposes, so it often depends on which point each game is in its story. star rail feels a lot more Dense in terms of how much worldbuilding goes into the main storyline, particularly because the divine beings are a lot more enigmatic than those in genshin, in which we interact with gods like they're regular people. star rail's portrayal of morality is also a lot more layered in my opinion, and the only characters whom we are supposed to see as blanketly bad morally are those who represent the ipc (yes, even the ones who are sold as lovable to us).

on that level, i think genshin's story is probably a lot more universally relatable, since its themes are much more representative of current social climates in ways that are (or should be) obvious, whereas star rail requires a bit more prerequisite understanding of narrative devices to truly make its points. inversely, i think star rail does a better job of critiquing macrosystems and topics like disability and capital that affect all social demographics, whereas genshin is better at highlighting social stratification on a micro level, such as class differences within a specific culture or nation (although fontaine was a categorical failure on that level). going back to relatability, i think genshin's cast often feels more resonant on a personal level, since their experiences are a lot more applicable to our lives than characters in a hyper-advanced universe spanning galaxies.

tldr tho i think both games are very earnest in what messages they're trying to send, despite being held back by both a gacha format and deeply ingrained racism and xenophobia (which isn't unique to these games but feels more noticeable given the caliber of their storytelling), so i tend to go back and forth on which i gravitate towards more! although part of me is still biased to a game with dehya in it :x