> Basic language dialects found in most 8-bit PC ROMs

As far as I know, MS only produced GW-BASIC and BASICA. While they existed, they had to compete with numerous other BASIC dialects on other architectures. After the XTs passed on, those dialects no longer existed.

Once the 286 came along, MS had to complete with Borland, and then later Watcom and Intel. I personally think Borland dominated the compiler landscape for at least a decade. If you considered Borland and Watcom both, only scraps were left for MS (one scrap being QB).

It wasn't until Windows 95 came along that MS actually came out on top.