No one came close to gmail's 1GB free inbox at the time. Which kept increasing and showed you at the bottom of the inbox. Plus it had amazing spam detection, and was stupid fast, and got better and better very quickly.

I remember having a gmail email was almost a litmus test to whether or not you were paying attention to what was going on in tech. Not having a gmail email indicated you might not be keeping up with the times.

Agreed on all your points! But I think offering a better service in an established sector is the opposite of "no competition" and being a "first mover".

Like how we would say a professional sports player playing against an amateur has no competition. Technically, yes, but effectively...

The context of the discussion is whether or not an "invite only" tactic works for building hype and launching a successful product. In that sense, I would attribute Gmail's success not to the "invite only" tactic, but to the fact that it was so superior that it had no competition.