How do i compare AMD and Intel CPU's, shall i compare sempron with intel dual core or quad core ?

As a rule of thumb

Compare "AMD's Sempron" to "Intel's Celeron or Atom"

Likewise Compare
AMD's Athlon to Intel's Pentium
AMD's Athlon II to Intel's Dual Core

and
AMD's Phenom to Intel's Core2Duo
AMD's Phenom II to Intel's Core2Quad