Since this is an ASP forum, I'll add that the UI in Access is pretty much meaningless except when you create the initial database, and for that SQL Server uses a nearly identical interface.
SQL Server is also more flexible and capable. Today you may not need, say, triggers, but you might very well tomorrow.
Here are more things SQL Server has that Access does not:
[ul][li]SMP Support
[li]Triggers
[li]Temporary Tables
[li]Stored Procedures (via T-SQL, faster and more capable)
[li]User-Defined Functions
[li]Views
[li]Integration with NT Security[/ul]
That said, I still use Access for low-volume sites on shared hosts because it's much, much cheaper (and often included in the hosting price). For anything else, though, it's SQL Server all the way.