Nugoo said:
I think the choice is usually between playing for free and not playing, rather than between playing for free and paying.
In which case the only ethical choice is
not playing. As the consumer, you are perfectly within your rights to decide that you are not paying the requested price for the product.
You are not, however, within your rights to make up your own price (free), and then play. You either pay what the seller is asking, or you do without. It has nothing to do with theft, it has to do with you being an arrogant prick, not respecting the time and devotion people put into their creations. Just because you can't see the software developer doesn't mean they're worth less of your respect and working time (as indicated by paying) than the plumber who comes over to fix your pipes. Sure, you might have been willing to go with that dripping faucet anyway, but that doesn't mean you shouldn't pay the guy.
You don't like paying for games? Fine, don't. Play free games. Play demos. Refuse to purchase things that don't have demos and let the creators know. But don't play games, refuse to pay, and then think "Yeah, well, I wouldn't have paid for that anyway". If you wouldn't have paid, you shouldn't have played. And if you do, at least understand what an ass you're being to the creator, and understand why some people think you're just a selfish little prick.