Well, maybe you need to configure your system.
I may be wrong, but it seems that the loaded driver for your video card is the
vesa, not the
intel.
For the vast majority of users, X on amd64 auto-configures successfully, so no further configuration is needed.
But sometimes, a etc/X11/xorg.conf file is needed.
Did you try to create one ?
You should read the
OpenBSD's FAQ to see how to configure xorg.conf
Edit : I just can't believe it.
I've just checked, there is no
section 11.3 in english in the FAQ ! 
But we've got it in french :
Configure X on amd64 and i386