If you are flashing the ROM from the recovery installed in the phone, you must manually "fastboot flash boot boot.img" after installing the ROM, if you loading recovery by "fastboot boot recovery.img" then you do not have manually flash boot.img, although doing so will not hurt anything.
Remember the ROM ZIP file needs to be on the SD card of the phone, not your PC. You "fastboot boot recovery.img", wipe everything, flash the ROM ZIP, and reboot... if that isn't working then one of those steps isn't being done correctly.
Also, are you sure they are bootlooping? How long did you wait? I have seen some ROMs take a good 10-15 minutes on first boot, maybe more... although it feels like forever. It always seems to go through my mind that it's taking too long and I need to pull the battery and restart because I missed something but it (almost) always comes up given enough time.