Normally the queue depth is at 64 I thought. Changing the queue depth would only help if your VMs would generate more queues then 64. For example, normally Windows has a queue depth of 1 normally.
you should never manually edit esx.conf as if you have extra whitespaces, bad characters, etc. the file wont be read
What you need to do for QLogic to increase the qdepth is
esxcfg-module -l (to see what module is loaded - should be qla2300_707_vmw)
So do this to increase to 128
esxcfg-module -s "ql2xmaxqdepth=128" qla2300_707_vmw
Then run esxcfg-boot -b and reboot (this will load the changes into esx.conf which will be re-read upon reboot)
P.S. QLogic has a queue depth that can be set 0 to 255. Emulex is capped at 64