In web development Is Asp.net MVC good or 3-tier Asp.net MVC project?

MVC is the recommended pattern for ASP.Net web applications.Visual studio itself give inbuilt project template for the MVC architecture. 

So many performance as well as design advantages using MVC. 

There are three tiers in ASP.NET MVC by itself.

1. Model: This is the place where the business logic and the data access for the application resides.

2. Views: Here you manage the things displayed to the user and it receives data from the Model classes.

3. Controller: The controller listens to the views for user input and communicates with Model classes if needed.

You have all the three tiers here already, but you can develop an application with three tiers physically also too, like each tier in a separate project. It's up to your convenience, that in what way you could develop and maintain an application.

The MVC separation helps you manage complex applications, because you can focus on one aspect a time. For example, you can focus on the view without depending on the business logic. It also makes it easier to test an application.

The MVC separation also simplifies group development. Different developers can work on the view, the controller logic, and the business logic in parallel. Reference (W3Schools.com)