to get rid of all the freaking Majong games?!?!?!?!? 
I think MAMEContentManager
www.mameworld.net/mcm can get rid of the Roms for you.
If you want to eliminate the games - there are a couple of options. If you don't have a frontend preference, download EmuLoader from
www.mameworld.net/emuloader and use it's parental lock editor to remove the games from the gamelist.
If you don't want the games in MAME, but want to use some other frontend, it is fairly simple to do, but requires a lot of steps.
First, learn to compile your own MAME - this is fairly easy from
http://www.mame.net/downmain.html (win32 compile utilities halfway down the page) and additional info here
http://www.mameworld.net/compile32/ (ignore the MAME32 stuff).
Next, you want to open up src\driver.c in WordPad and remove (or comment out by typing // at the start of the line) the games that you don't want listed. Easiest thing is to search on mah, but you'll also find tomahawk and dimahoo, so don't do a global replace.
Then Recompile and these games will not show up in the game list.