So I see that on the item shop you can 'buy' a game system, meaning you can play all games on that system for free. Aren't they already free? As an unregistered member, I was able to play any pokemon game i wanted as long as I wanted as often as I wanted. Does that change when I became a member and if so, why would that be? *confused*

Don't worry, everything is free. Playing games costs Viz, the money of the site. You get so much Viz free just for logging on and can get Viz from posting, writing reviews and so on. Buying consoles in the item shop (with Viz not real money) will let you play the games for that console and not pay any Viz.

Well the thing is, the games are free, but only limited. I just checked this again a minute ago on Super Mario World being logged out. The text in the title bar of the game window that opened, said that I had "7 free plays remaining". So I started the game seven more times and from then on, I couldn't start any other game, the pages said "Sorry but you can only play 7 games per a day as a guest.
To contine playing games you must Register for a free account or Login to your existing account. "

And I just noticed, that means you can play seven times every day for free as a guest.
However I think saving and loading is disabled without account.
This is probably to encourage to create an account. Yes, you'll have to pay Viz for it, but that shouldn't be a problem, since there are a lot of ways to get it. Even the 100 Viz you get when logging in is enough for lots of games.

Oh ok. That now makes sense. Thanks guys!

*Creeps out of nowhere and closed the thread since the question has already been answered*