1. Only suggest porting open source projects or creating original projects.
Games and applications that have no source code available are impossible to port.

2. Keep in mind the Vita hardware limitations.
PlayStation Vita has 365 (+26) MB of RAM available for applications, 112 MB VRAM, and 500 MHz CPU. xray-16 (S.T.A.L.K.E.R.) is an example of what's impossible to run on the Vita.

3. Do use the search feature.
There are more than 180 entries in this database already. If what you want to suggest is possible, there is a good chance that it's here already.