Best ASP.NET reporting engine with custom reports creation ability

DevExpress XtraReports Suite.

A report is simply a class, no web services or rpt files involved.

http://www.devexpress.com/Products/NET/Reporting/

I've worked with all the major reporting tools and each has their plusses and minuses. About the only "plus" on SQL Report Services side is that there's no additional $$ expenditure above the SQL Server license. The downside is that the report designer is probably the most child-like of all.

Crystal has been around forever, some love it, many hate it, it does the job, but has a serious price tag involved if you want to use it for anything other than personal use. And the web reporting server for it is VERY expensive.

ActiveReports, XtraReports, Telerik all have good products and all are being actively improved (at different speeds, of course). Each has a web viewer, but they don't include the rest of the things you might want from a web reporting server.

And if you find you really want an enterprise-class web server option for Crystal, ActiveReports, XtraReports or Telerik reporting (or any other report designer, for that matter), that's now available from www.versareports.com.

If you have Microsoft SQL Server as Database, so you don't need to purchase License for support of SQL Reporting Services, but there is an issue with SQL Reporting Services, SQL Reporting services only Compatible with IE. check these links ...
http://msdn.microsoft.com/en-us/library/ms156511.aspx

SQL Reporting Services - Print Button not shown in Mozilla

On the other hand, If you use other than Reporting Services, You need to purchase License.