Legacy is - they can create quite good looking humans, awesome animals and that's just for kiddie game. And ohh, they have engine who can handle that.
I know ZT gets some loathing due of size limit (possibly MS QA inflicted), and simplistic menus (for me they seem to be very ok for console game). Still, tech is there, and FD has some people with serious skills on-board.
So planetary landings in a way David has envisioned them suddenly doesn't seem so far fetched idea.