I remember Netscape 4. In fact, I was using it semi-regularly (albeit on my Windows 3.1 computer) as late as 2003.
Although it wasn't quite as lightweight as Netscape 3 (which was undoubtedly their high-water mark), it was generally stable and ran just fine on a 486.
It had none of the security issues that Internet Explorer 4 invited by going above and beyond the definition of what a web browser should do.
If it crashed, it seldom took the whole system down with it as IE would always do.
It didn't take the entire system hostage. It left the Windows shell well enough alone. It was uninstallable, like a normal application.
Its rendering capability was no worse than IE 4's. (If it seems worse now--and frankly, most people haven't used IE 4 in years so they don't really know--that's only because IE got ahead of it in rendering capability after Netscape had its air supply cut off and was in a mad scramble to do anything other than fade away without a trace.)
It was a more robust browser than IE 4 in practically every way. And if Netscape had been able to develop the software in a more natural manner (a la version 1-3) without a monopolist breathing fire at their heels with blatantly-illegal marketing practices, I'm sure it would have been better still.
(And before you claim that IE won the Macintosh market "fair and square," remember that Microsoft threatened to discontinue Office for the Mac if Apple didn't bundle IE as the default browser on its systems.)