I have another hobby (currently moribund while I work on publishing stuff) that involves programming add-ons for the Orbiter Space Simulator. This is not a game persay but rather a simulator similar to Microsoft Flight Simulator.
It can be used by people of different skill level and interests. The trick is that many of the default vessels are semi-realistic in that they are way overpowered compared to what we can really build. So they are lot more forgiving for novices getting the hang of orbiting and travelling in space. A realistic Space Shuttle is included as well as an orbiting International Space Station.
There are huge variety of add-ons at the Orbiter Hangar from my ultra realistic Mercury and Gemni to the fanciful. Note that Orbiter 2010 just has been released and many of the add-ons, my own included run better on the previous version Orbiter 2006. It still avaliable for download.
To me the Old School Renaissance is not about playing a particular set of rules in a particular way, the dungeon crawl. It is about going back to the roots of our hobby and seeing what we could do differently. What avenues were not explored because of the commercial and personal interests of the game designers of the time.