I believe stockfish is the strongest native engine. Best is a little more subjective, but a lot of people like mac chess explorer which is commercial, and chessx is also available, which is quite nice as well (although I don't believe the binary package has been updated in quite some time).
If you have an older version of os x (before lion, I believe) sigma is also available and is now free (used to be commercial).
Depending on rating list, critter (which also has a native os x version) may be stronger than stockfish, but they tend to be really close and just a bit behind houdini3.
or virtualbox if you want a free alternative, not that the difference between stockfish and houdini3 is really all that relevant for most players.
I believe vmware product for mac is called fusion, there's also a product called parallels which is similar (or there used to be -- I mostly switched to virtualbox in the past few years).
The free open source program ChessX version 0.9.4 was recently updated in December 2012 http://chessx.sourceforge.net/?q=node/3.
You can use it with the free engines Critter, Stockfish or Komodo 3 for the Mac.
I also post more recent updates to www.box.com/chessx
If you want a commercial product, Hiarcs Chess Explorer is by far the best commercial chess program on the Mac.
Thanks a lot mates!
I was looking for a program like ChessMaster which has some chess classes, those nomes fit it well.
You will want a database manager with your chess engine. I strongly suggest you look into Mac Chess Explorer bundled with HIARCS 14 engine. This combo is the best on the (mac) market.
http://www.hiarcs.com/mac-chess-explorer.htm
-Izmet
The free open source program ChessX was just updated to version 9.6 http://chessx.sourceforge.net/?q=node/3. Its a database manager and PGN browser that runs on both Windows and Macintosh.
I was just about to ask about chess on the Mac, being recently converted to a current 27" Intel i7 iMac as well as an iPad 4. I found HIARCS for iOS for only $9.99 which seems like a steal for an iPad/iPhone! As far as my iMac, I'm disappointed some of the top programs (Fritz, Rybka) don't support Mac OS X (I'm on 10.8 - Mountain Lion), and also that Sigma seems to have petered out with Snow Leopard, but I'm happy to have found this thread with some alternatives!
I'll be checking out the Mac Chess Explorer and Chess X frontends along with the mighty HIARCS engine. Thanks everyone for the suggestions. If you have any more, please share! Chess AND Mac fanatic here 
HIHI,
Which is the best chess game for mac in the market?
Thank you,
Rodolfo