There is a lot more to consider aside from minimum system requirements...there are much bigger issues like:
1.) CPU Architecture
2.) Target OS and it's libraries/frameworks
3.) Porting research
DOOM has been ported to TONS of things...someone even got it to run on a printer IIRC, while half life exists on one architecture. Unless someone has lots and lots of time to spare you're not likely to see it.
There is an open source alternative to goldsrc called xash3d, it has been ported to arm and with a lot of work it could run on the 3ds. The real question is if someone is willing to port it.