Someone created modified version of Desmume with option to increase internal resolution check this out:
https://www.youtube.com/watch?v=lZgrx8pp0yw
https://www.youtube.com/watch?v=Q8JlPAayDHs
Some comparison screenshots + download link:
http://desmume-ds.blogspot.com/
(SoftRasterizer)
[3x] High-Quality Mode
Unofficial Desmume with internal resolution increase option
Sorry if my English is bad, I'm French !
Re: Unofficial Desmume with internal resolution increase opt
Looks amazing, hope we'll see something similar in drastic at some point