Yes, he wanted to play for Wales because he is Welsh. He wouldn't swap any amount of World Cup appearances for the sake of turning his back on his country.
Yes he would have been a top player for England, but then again so would Diego Maradona, I don't quite see your point Aussie, the guy is Welsh. Yes Welsh cricketers can play for England, but :
a-Cricket is a different game to football, with different rules
b-In Cricket, Wales doesn't have its own international side, or at least not a fully afilliated one. Instead it is part of the ECB. In Football, Wales is a separate entity. It has its own team. If Welsh players were to play for England they would have to cease having a football team of their own, and that'd leave pretty much every Welshman of the last 15 years, except Giggs, and Ben Thatcher, with no international football career.