even if those are the specs for "today", my answer remains. .NET and SQL Server.

Using SP and no change tracking, right? ;-)

Seriously, you're just describing the value proposition you offer and with which you're comfortable. IOW your advice is to suit *you*, not necessarily the customer.

Example: what if the customer already has 10 Linux apps and little in-house Windows Server expertise. Is NET with SQL Server still best for that customer? What if they have 1,000 spare Oracle licenses and a DBA but no SQL Server licenses or expertise for this 100-seat app. Is SQL Server best for the customer? What if they have a strong Java and/or MySQL in-house team. Is NET definitely best for this customer?

It seems you already know the answer before the customer even describes themselves. ;-) It's not quite like using a hammer to drive a bolt since you are correct that your preferred tools can do the job (and fwiw I'd use SQL Server as well in this case unless the customer doesn't want to pay for licenses, in which case MySQL) but IMHO it's intellectually unsound to only ever have one answer. Up to you, but that's how it seems to me.