"Proper d20?"
All of the above.
What am I more likely to buy?
2, 3, and 4. Adventures are those things that I'm either building myself or people are practically giving away for free.
What I COULD use, are more adventures for unique settings. I see tons of support for D&D, almost none for other settings. Modern is next most supported, through 3rd party and WotC, but I wouldn't mind seeing more heavy sci-fi adventures, superhero adventures (I loved GR's Time of crisis, and wouldn't mind seeing more things a little over half that size), and speculative fiction adventures. (I'd LOVELOVELOVE to see Black Company adventures, but I understand why GR can't do it due to licensing.)