American pie and Hangover

I heard that the only first part is good and other second and third are just cash grab , what should I do? Should I watch all the part or only first one

And i just watched 4 part of the American pie

1) American pie 1
2) American pie 2
3) American pie wedding one
4) and American pie reunion

And I heard that there is also prequel of American pie, should I watched them all ?