So their must be a special incentive to make me buy it again and making ME1 and 2 gameplay wise like 3 would do that (too costly or not). Not interested in same rehash with a little better visuals.
Even putting aside the cost, how would they make ME1 play like ME3? They're designed completely differently. ME1's entire combat system is built around the stuff that isn't in the later games, not to mention all the non-story stuff. I feel like people who ask this haven't stopped to think about how much work it would involve.
Would it mean getting rid of skills, putting in ammo packs, putting in ME3-style grenades, adjusting all the enemy types and encounters for new weapons and powers, getting rid of heavy weapons in ME2, changing the entire weapon upgrade system to ME3's simplified model, changing armour, changing powers.... and then trying to balance everything?
Then how would they deal with the story and non-combat stuff that relies on skills and features that weren't in ME3, like decryption/electronics and the anti-Thorian grenades on Feros? How would they make quest rewards work if there are no more weapons or upgrades? What would all the Citadel shops sell? What use are credits? What would they put in all the boxes/crates/upgrade packs around the levels and on uncharted worlds?