Unfortunately, yes. While it has been discussed here for a long time and was mentioned a lot in tech news stories when Mountain Lion first appeared, Apple itself has never warned potential upgraders (i.e., no warning given in the App Store) that Power PC apps are not supported in Mtn Lion. You are one of multitudes who have found it out the hard way. Not that that makes you feel better but you have plenty of company.
If you have your old OS X disk, you can make a dual-boot machine and boot into the old OS to use your Power PC apps.
There are several posts here and elsewhere about how to do it. Here is one:
Here is a post that I assembled for another who needed to continue to run his PowerPC applications in Lion/Mt. Lion:
Unfortunately you got caught up in the minor miracle of Rosetta. Originally licensed by Apple when it migrated from the PowerPC CPU platform that it had used from the mid-1990's until the Intel CPU platform in 2006, Rosetta allowed Mac users to continue to use their library of PPC software transparently in emulation.
However, Apple's license to continue to use this technology expired with new releases of OS X commencing with Lion (and now Mountain Lion). While educational efforts have been made over the last 6 years, the fact is that Rosetta was SO successful that many users were caught unaware UNTIL they upgraded to Lion or Mountain Lion.
1. If your Mac will support it, restore OS X Snow Leopard;
2. If your Mac will support it, partition your hard drive or add an external hard drive and install Snow Leopard into it and use the "dual-boot" method to choose between your PowerPC software or Lion/Mt. Lion;
3. Upgrade your software to Intel compatible versions, or find alternative software that will open your data files;
3. Install Snow Leopard (with Rosetta) into Parallels:
[click on image to enlarge]
Full Snow Leopard installation instructions here:
NOTE: STEP ONE of the instructions must currently be completed on a Snow Leopard or Lion Mac and the resulting modified Snow Leopard.cdr install file can then be moved over to your Mountain Lion Mac for completion of the remaining steps.
NOTE 2: Computer games with complex, 3D or fast motion graphics make not work well or at all in virtualization.