NyQuil
Big F$&*in Q
BioShock is great largely because the focus wasn't on being a shooter. It's the RPG elements that really make that game, IMO. If it had ditched those and focused on shooter elements, it would've been a far more forgettable game. I suspect that most people who are either lukewarm towards it or hate it are judging it as a shooter and not appreciating that being different from most shooters is what makes it so great.
I found "significant tactical advantages based on weapon/plasmid choices" to be one of the game's strengths. It made a big difference which ammo you were using. For example, anti-personnel rounds did about twice as much damage to humanoids as regular rounds did, and armor piercing rounds did about twice as much damage to armored/machine enemies. Doing research by taking photos added more damage on top, as well as helped you to know which ammo types should be used against which enemies. Finally, different enemies were much more susceptible to fire, ice, electricity and so on. I actually found the game to be stronger in this aspect than many "truer" RPGs like Fallout 3 and Oblivion/Skyrim, in which you don't have as much choice in which weapons or ammo to use in encounters because you already spec'ed yourself for certain weapon types and decided which to carry with you.
I enjoyed it for the story and setting but as far as gameplay goes it was pretty linear.
Mass Effect did offer a lot of tactical differences in terms of the class that you could play, and you had the option of doing side missions or not, doing planets in whatever order you choose.
It was still a close vote - Bioshock was a very unique game but I got more out of the recordings and conversations than the actual combat. It had a few Half-Life type scripted encounters that would startle you but after a few levels it got pretty reptititive IMO.