reggiebDid a search on Best Buy, they only sell 3 Sound Blaster products... And the E5 for sale here isn't one of them. The E5 has more features than the G5 ;)
The E5 and G5 both have the same Amp and DAC, the G5 has a red LED that changes brightness as you change the volume, but the E5 has some things the G5 doesn't: a battery, Bluetooth, stereo mics, a stand with a screw-mount, supports powering two headphones at once, and USB Host Mode for a direct wired digital connection to a smartphone or tablet. Both (now) can also support a pretty hardcore virtual surround experience with PC and Mac games, connect smoothly with game consoles (with what I would call a more "casual" surround experience, or stereo), and do a pretty great job with music.
The G5 is for home use, the E5 can serve just as well at home but also is useful on the road. Supreme utility on the E5.