That specification is far too loose to give any real recommendations!

I suggest you try exploring http://www.keil.com/dd/search_parm.asp with some appropriate parameters to narrow-down the field, and then take a closer look at whatever seems hopeful

Fingerprint analysis can be an extremely demanding application - so it depends on exactly what you are intending to do!
eg, will you be using some bought-in susbsytem to do the hard work of recognition?

The raw processing is unlikely to be a job for an 8051 - more likely an ARM7 or even ARM9;
But, if you have some "intelligent" fingerprint module, an 8051 could well be OK - although not suited to extensive database lookups for authenticating "allowed" prints...