Continental did order the B767-300ER in the early 1990s, but the order was cancelled very close to delivery as part of the airline's bankrupcy at the time. The aircraft were built and now fly with several different operators - which is why there are B767-324ERs flying around despite Contiental never having operated it!
Second time around they probably decided the capacity of the -300ER was too close to the -400ER to justify the operation of both types. The -200ER fills a very different role, on thin long-haul routes which have a strong demand for Businessfirst or cargo capacity which make them worthwhile over the 757, which in CO
config has the same seating capacity as the 762.