There's a big difference between OS 9 and OS X and hardly anyone develops for OS 9 any more so finding the same functionality in a new app for an app under a dead system will be very difficult. You can't expect developers to keep supporting outdated technology forever. It's easy to be complacent about your own choice but you have to think how much a headache developers would have if they had to support you all. Most quite rightly just stop developing for OS 9 and all developers should. My dad is the same way and he still insists on using OS 9 all the time and complains when things don't work and then says 'well it works in OS X but I want to use OS 9' and I just tell him to stop being an ass.
It's not about forcing anyone to do what they don't want - a lot of people feel that anyone saying to upgrade is attacking their choices and so they dig their heels in - when in fact it's more like tempting people over to a better system. It's a big change but one for the better so please seriously consider a permanent change.
The only thing I can suggest that might come close to Google Earth functionality under OS 9 is the online Microsoft website:
http://local.live.com/default.aspx
I only got it to work in Firefox. At first it looks like an atlas but instead of providing blurry images for undefined areas, Microsoft uses an atlas.