In this era 3Com was still the gold standard, but intel eventually dominated the market because they integrated 100mbit and then gigabit on the PCH relegating any margin in the expansion card market to servers. As someone that has worked on a lot of Intel drivers I always find Intel being put on a pedestal to be a little amusing, they have a tendency to make a lot of gaffes in silicon and sometimes these reappear in followup designs. It's certainly not bad, but I would place Intel networking about mid-tier historically and today.

Realtek then dominated by being cheaper and simpler than Intel; they had the majority of the NIC marketshare (70%+) in the late 90s and early 2000s.