Okay

Farfetch'd was a standard Haymaker card. He had pretty good stats, with 50 HP, which was far superior to Nidoran. His attacks were also pretty good. The ability to do 30 damage on turn one was rare, especially for one colorless energy. Then, if that was successful, he could then have a DCE attached and deal 60 damage on turn 2! That was great, and could down even stage ones, let alone just about any basic. Plus, he was one of the only good cards with resistance to fighting, a common type. He was a staple card of his time. Plus, there weren't too many good electric pokemon, so combined with 'Buzz and 'Chan, there was an unstoppable threesome.

Since Scyther's creation, however, Farfetch'd has been used less. His weakness to a less commonly played type, his extra 20 HP, and no retreat cost made him a more favorable choice than Farfetch'd. As of now, Farfetch'd is pretty extinct. We still love the little onion duck, but Scyther is more reliable.

I hope that answers your question. Farfetch'd, like everything good, was great for it's time, but lost value in the future environment. But think of this: It took them almost a millenium to make something better! :-) Goodnight everybody!