Forbidden Kingdom is terrible as Kung Fu goes, it has a few semi decent fight scenes but overall its rubbish. The lead american actor is terrible.....only redeeming feature is Jet Li as the Monkey King.
Some to watch.
Drunken Master 1 and 2 (make sure you watch the Cantonese version of DM II as the American version has ruined music and sound)
Dragons Forever (Jackie chan, Yuen Biao, Samo Hung), some excellent fights.
Kiss of the Dragon (Jet Li)
Fearless (Jet Li)
Police Story II (not as superb as the first but still good)
Operation Condor - Armour of God II (Jackie Chan - stupid plot/crap acting/but some nice fighting)
Fist of Legend (Jet Li - probably his best kung fu film imo)
There are plenty of other good ones.
Stay away from rubbish like House of Flying Daggers/Hero, arty farty wires and nice visuals instead of proper action.