Without a shadow of a doubt Chessmaster is the best. Fritz is a fairly intelligent engine but I found if overly messy to look at. The teaching elements in Chessmaster are far superior in my humble opinion also.

Hey johnny, you may want to try out these websites!

http://chesscentral.com/chess_download
http://shredderchess.com
http://hiarcs.com
httphessopolis.com

fritz 11 can do anything chessmaster can do and a million things more. to describe it as a “fairly intelligent engine” is a wild understatement. i consider myself an intermediate player as well and i like fritz. but osu is probably right that chessmaster probably has a clearer format. shredder and hiarcs are also top engines, but fritz is very popular. http://chessbase.com runs fritz-compatible tutorials.