Ejb is a EJBCntainer. servlet and jsp are webcontainer.
Ejb is business logic . servlet and jsp are presentation logic.

EJB used as persistant layer.
JSP used for presentation layer.
Servlet we can use as controller.

In ejb u hv many inbult feature like "Transaction 
Management", "Security Management" etc. U just hv to call 
those function for managing all this thing. All the things 
r managed by/depends on application server.

In Servlet/JSP for Implementing all this thing 1 has to 
write complex codes.

Important using EJB in small application is tradeoff.

EJB is a distributed component model for developing
secure,scalable, Transactional and multi user component.
EJBs are reusable software units containing business logic.
EJBs allow separation of application logic from system-level
services thus, allowing the developer to concentrate on the
business logic.EJBs reside in EJB container. needs
Application server.
Servlets are serverside components involved in request
response process. JSP- Java server Pages an extension to
servlet technology. JSPs are text based documents involved
in request response process. at run time JSPs are converted
into servlets. servlets , JSPs resides in web container. one
can use JSPs for presentation, controller as a servlet and
business components can be easily managed as EJBS.