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. 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.