Mass Effect is an excellent RPG with fun gameplay and one of the best stories in video games.
Gameplay
You play as Commander Shepard, who quickly becomes a "Spectre" early on in the game. You fly around the entire galaxy helping people with quests and trying to save all life. A lot of the gameplay revolves around shooting, which plays out fairly well. I didn't have any major complaints about the combat, and there are tons of upgrades to your weapons and armor for you to play around with. There is a duck/cover system that is pretty standard, nothing extraordinary, but definitely functions as advertised. There is also a lot of options for you in this game: this was one of the first to let you play how you wanted: if you want to let people die, you are free to do that. If you want to explore every single planet, gather every resource, and help every single person who asks you, you can do that too. This game can last anywhere from 15-30 hours or so depending on how much you want to do. I ended up with 21 hours and did most of the sidequests in the game.
Unfortunately, the worst part of the game is the Mako, which is your little space car you drive around planets. It drives like there's some sort of trampoline under it. Every time you hit even a minor bump, it goes flying off chaotically in a random direction, and it's hard to control the dang thing even on flat terrain. There are mods for this which I highly recommend, because this thing drives like a POS and makes many of the missions downright annoying. Many sidequests require you to drive it around, and the main story requires it quite a bit.
The sidequests are all worth doing, you won't see any "kill 5 rats" type sidequests in this game. The stories are interesting, if short, and worth checking out. The only complaint is that the sidequests re-use the same exact maps, so you feel like you've been to this facility/area/world before....because you literally have. That is a frustrating part of the game, I'm not a developer but they could at least have made a few more maps to make the sidequests seem more realistic to play through. The mini-map could have also used an actual map instead of just red dots on the screen, but that's a minor complaint. Lastly, the elevators take FOREVER....for no reason whatsoever. You will quickly become tired of taking elevators through the Citadel. Luckily a fast travel system becomes available early on and you can avoid most elevators, but that doesn't excuse them taking a full minute to go from point A to point B.
Story
A masterpiece of a story is given to you here. It's got ups/downs/twists/turns, everything you would want from a movie or game. It's especially fun for anyone who live sci-fi, I felt like I was in Firefly the whole time I was playing. You can play as a good guy or bad guy, or somewhere in between if you wish. Your decisions literally change the course of the game, and you can't save everyone no matter how hard you try. It's a good lesson to know that you are going to have to sacrifice no matter what options you choose, and I appreciate that about the game.
You can romance someone if you wish, but it's not required. It honestly felt kind of tacked on, but I obviously did it anyway. The sidequests are varied and interesting and add a lot to the story and characters. But the main story is excellent. I couldn't wait to finish the game to see how it all played out, and now I know I have two more Mass Effect games to play to see the full story. You will grow to actually care about the people in the game, which is a rarity. This is one of those few and far between games that makes you really feel like an actual hero out to save the galaxy, and it doesn't feel forced or stilted at any point in the experience. I thought it was the perfect length for what it was: it's not going to be a Skyrim or BOTW that you play forever, but the story is enough that you want to see it through without taking too much time away from it by playing random sidequests.
Music
The ending track is especially great. The music when you look at the galaxy map is also excellent. The rest of the music fits well with the atmosphere, but isn't something you will likely listen to outside of the game.
9/10