As with most games with sequels, it would benefit you to play the previous games but not necessary. I have not played Bioshock Infinite yet, but I played the first two.
Bioshock 1 was a masterpiece of storytelling and I would feel bad for any gamer to miss out on playing it. Really. It's that good.
Bioshock 2 was good gameplay, and worth the play, but overall a 'meh' product.
I can't wait to play Bioshock Infinite, but I do not have the time at the moment. I know it's going to be epic. Again, if you've played first-person shooters, you'll have no problem picking up Bioshock Infinite without playing the first two. I'm sure Bioshock Infinite has a story that can stand by itself without playing the first two, but not playing Bioshock 1 (maybe even after Bioshock Infinite) would be doing a great disservice to yourself.
As for PC vs. Console, it depends what you like. I like console games when I feel like being in my living room on the TV instead of being holed up in my den on my PC. But... I love PC games because their graphics are extremely better and the versatility offered by the keyboard/mouse combo over a controller. I will probably get Bioshock Infinite on PC.