Questioning the "overall weakness" of the NL Central

I'm getting pretty sick and tired of "major" media outlets comparing the NL Central to the retirement home's bowling league. ESPN and Baseball Prospectus both had pieces about the Cubs today questioning the competitiveness of the NL Central (basic gist: "The Cubs suck, yet are still 2GB"). So I did some looking...

The NL Central, outside of the division, but within the NL, has a winning percentage of .517 (109-102).

The NL East? .462 (90-105)
The NL West? .522 (95-87)

Or how about the American League, again: outside the division but within the League?

AL East: .525 (105-95)
AL Central: .428 (89-109)
AL West: .528 (94-84)

So basically we see the breakdown as follows, in order of winning percentage:
AL West: .528
AL East: .525
NL West: .522
NL Central: .517
NL East: .462
AL Central: .428

So we see from here that the NL Central is 4th among the six divisions in winning percentage outside the division, but still well above .500. The weakest division? Looks from here to be the AL Central, trailing the NL East. But don't tell ESPN, they won't like that.

I will say this: If you think this is flawed, let me know why, and we'll rework it. I don't want to be accused of using numbers to suit my own purposes...