How is it competition?
You can't see a Mets and a Yankees game at the same time, you know.

Shea Stadium is not a great ballpark, it's a cookie cutter piece of crap
At least we agree on something....
they needed a new stadium. The Yankees had a great stadium, with history and tradition, and would have been completely fine for many years. You think that if the Met's got a new park, and the Yankee's didn't, all of a sudden attendance would drop for the Yankees and they would loose money? No way, in any way shape or form. Who fills up Yankee stadium? Yankee's fans. It's not like they would all say, lets go to CitiField because it's brand new. They would still make money. It's still one of the largest, if not the largest capacity parks in the majors. It's not like they needed more seating.
The fact is the Yankee's did not need a new park. I honestly think that if the Mets were not getting a new park, the Yankees would be in Yankee stadium for years to come. The draw of Yankee Stadium is it's history and tradition, and that is now all lost I believe, just replaced with a copy.
You're a Sox fan who hates the Yankees. What the hell do you care what happens to Yankee Stadium?