The RE20 is fine for in-studio use but not for the field.
As for an interview mic in the field it depends on your use. for most face to fact interviews they will use an omni dynamic. Electrovoices and Shure's are the most popular. However in a noisy interview space, particularly like say a sports locker room, they will use the narrowest dynamic they can find.
I second the M58, the frequency response is much better than the 635a and the longer handle means you don't have to shove your hand in an interviewees face. The 635a is in second place too though and a lot cheaper. You can apparently get a 635L which also has a long handle but i havn't seen one.