Halo reach had the best forge maps by far you had the huge canvas of options called forge world.
This video explains all the problems of halo 4 forge though
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&cad=rja&ved=0CDAQtwIwAA&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DKMaKVDEBqoY&ei=W4hbUryjGISi0QXm2IGYCg&usg=AFQjCNH46SZLADNHXyEBE9jdXSjAE1_wbg&bvm=bv.53899372,d.d2k