Yes, obviously. Always have done. I'm using one now - Camino - and there's Firefox, Opera, and plenty of others. I've owned Macs since my first computer, one of those Candy iMacs about 11 years ago. Other people make software for Macs too, by the way - you can get stuff to do just about anything either free or purchase - same as for Windows, really. And though not as much (the marketshare is much smaller) probably more percentage-wise compared to market share. The software often tends to have a longer life too.
Anyway, re Steve Jobs, his vision changed the World, IMO, in terms of consumer electronics and gadgets. He wasn't not the only person to do that, but he was one of them. He changed mine - the ease of use of (my) computers, of having all my music with me, and of having a portable, user friendly little phone thingy to do all kinds and so on - they're all down to Steve Jobs and Jonathan Ive, really.
I'm sure other companies will make terrific gismos too. It doesn't matter, though. I know that if I buy an apple gubbins I'll instinctively know how to work it, it'll be well made and it'll do what it's supposed to do without quirks or crashes or viruses or whatever. The user experience is very satisfactory, and that's what really matters to my choices.
Not sure about Microsoft being "open" by the way. I percieve the opposite to be true, but don't actually care and it doesn't matter.
This