Both programs support Gedcom v5.5 (the latest version of Gedcom) so one exports data in gedcom format from Generations and imports it into FTM.
Note that EVERYONE interprets Gedcom slightly differently (sigh), so you may find it useful to use Gedcom Explorer (shareware, http://www.gedx.comhttp://www.gedx.com) to take care of some of the minor bugs that show up in Gedcom transfers.That program has a large number of pre-defined filters that assist in the mapping of gedcoms from one program to another. You may also customize it.
Personally I don't like the FTM user interface.There are differences in reports and charts between the programs (pluses and minuses).
I have not yet found a genealogy program that supports all of the features I want.I don't expect that I will, nor do I expect other users to want the same features I do :-)