It would be nice if they made it a feature or option when building the romlists since they're using thegamesdb.net to get the info and the story/synopsis info is there. You get the story/synopsis info on Emulation Station scraping on thegamesdb.net.
I have tried to import .xml files that have the info from other frontends using the command line but when the romlist is built it's doesn't have the story/synopsis info in it.
Another option would be to use a newer version of MAME where MESS is combined. The history.dat file has the info for the console games but the names are MAME specific and not common to other emulators.
One you have the story/synopsis info in the romlist file you still need a way to present it. This would mean you would need a layout that would show it. There are some layouts that support the info but I think most are using the history.dat file and using MAME. I find many people (especially cabinet owners) only use/care about MAME.
There is also this thread
http://forum.attractmode.org/index.php?topic=656.0 which I tried to follow up on but haven't heard anything.