Mass Effect had a lot of great moments where your choices changed the story:
- Kaiden vs Ashley in ME1
- Spare or kill the Rachni Queen in ME1
- Talk Wrex down or just kill him
- Helping squadmates in side missions to determine who survives the final mission in ME2
- Curing or not curing the Krogan in ME3
- Whether or not you make peace between the Quarians and the Geth in ME3
- The 3 (or 4 if you had the DLC) choices at the end of ME3, especially when they made them more complete with the Director’s Cut