This is personal opinion but the following map seeds I found to be good:
187963896
87814253
956452604 (excellent though you start a little ways from the river)
I found this 1 to be fair:
31121968
These are all large valley. Hope these help.
More map seeds (these are map seeds I find listed on other sites that I try out)
Note:I use the unlimited mines and quarry mod so these seeds are mostly flat valley with not a lot of lakes, rivers and hills.
Good:
87514253
328800782
0788
90640792
902808712
Fair:
413316242
741653350
31244676
thanks you for posting :)