However, I think it is largely a mistake to judge software that was state of the art from 15+ years ago by today's standards.
In those days, most databases didn't really handle replication particularly well. Notes was the most fully-featured in that respect.
In addition network speeds and bandwiths were lower than they are now, so it wasn't really feasible for a global company to have everybody hit a single database instance.
Lotus Notes programming was simple, so if you could write a Lotus or Excel macro, you could create a database for your team. This made it popular for semi-technical end users.
It also pre-dates HTML, so web browsers and thin clients weren't really available.
Having said all that, I'd still take Notes over Sharepoint :-)