Tele is easier to obtain with four-thirds due to the 2x multiplication factor...getting wider is a lot harder and more expensive (so far).
For instance I own in OM mount 80-200, 500mm, and a OM 2x converter giving me up to 1000mm. I tried an OM 16mm fisheye, but it looked just as wide as the 14-45mm set at 14mm, and the fisheye effect was cancelled out! I also own some OM primes, 50mm and 28mm.