I guess it depends on your measure. Personally, the Ballmer era represents Microsoft going from being "the" software company to just another dying giant that wasn't relevant to me. I used fewer Microsoft products in 2014 than I did in 2000 when Ballmer took over. Sure, they expanded the product categories they competed in, but any company with that kind of capitalization could have chosen to do the same.
You don't, but companies sure do, and they're the ones with deep pockets.
Microsoft is clearly continuing to find success in an enterprise space that had its addressable market grow astronomically during Ballmer's tenure.
At the same time, they went from absolute dominance in the 90s software market to having a smaller share of a much larger enterprise market today. Is that success? Maybe. Was it due to Ballmer, or was it inevitable? Also unclear.