I enjoy the mystery around the galaxy in ME1. I enjoy the interactions in ME2 the most. However it's a TERRIBLE TERRIBLE sequel. ME3.. Honestly It's disappointing compared to what came before, however the multiplayer was some of the best fun I ever had. Then they come out with Andromeda which has some weird retcons or interference with ME3s lore which boggles my mind. Pick a lane Bioware!
Honestly I'd reccomend the original trilogy. After more than 10 years I have learned that if you are super into ME then its best off not digging too deep if you enjoy it! I dont even go into detail pointing out the problems anymore as I dont want to spoil anyones fun! lol