What kind of flying are you looking to do with it?
For a sedate, putt-putt around the sky bipe, look at perhaps a Kyosho or Gee Bee Tiger Moth, Concept Models Fleet, or a Jenny. There are several ARF versions of the TM around. Jenny will most likely be a kit only. For military types, most anyone's version of the WWI SE-5A is pretty easy to fly, and is easier to get to balance correctly without a lot of noseweight.
For a tear up the sky type bipe, it's going to be hard to beat the Goldberg Ultimate. It's a builder's kit, but it's not too bad to build. It flies beautifully, and with modest power, is easy to handle. There is also the Aeromaster bipe, or one of the Stearman kits/ARFs.
Of course, there is always the electric parkflyer type stuff, like the GWS series Tiger Moth. Dead easy to fly, and very inexpensive.

Hope this helps.

Rick