IE4 was better than Netscape communicator but not significantly. Before (IE3 and below) things were a lot more even. However by IE4 MS had already won the browser wars. It was a fair while after that point when AJAX became a thing (and Netscape and Opera did support a competing API to XMLHttpRequest btw). The problem with IE was that it wasn't standards compliment, only ran on Windows desktop and Mac (even Windows CE didn't really have a decent working version of IE) and even with their lack of regard for the standards offer very little innovation compared to the 10 years they had leading the market. Think about how much the web advanced once Firefox and Chrome gained traction and how far behind IE quickly got left, then tell me that what Microsoft did for web was a positive thing.
Real Player and Flash were cross platform (albeit Flash outside of Windows was and still is garbage). ActiveX was Internet Explorer on Windows desktop only and Silverlight was only partially cross platform (parts of Silverlight was ported to OSX and only OSX so it's a bit of a stretch to even compliment Silverlight for being "partially" cross platform).
For several years it was the best browser available. Invented a lot of things, including DOM and XMLHttpRequest.
> ActiveX / Silverlight and other MS web lockins
Everybody did that. Have you forgot internet with A/V streaming locked to RealNetworks, and vector graphics and animation locked to Macromedia?