Needs vocals.
There isn't too much to say here, as its a pretty good song. However, there isn't really anything that makes it very interesting. It kinda drags on, and would be majorly improved with vocals. At about 1:00, it got pretty messy, but got better soon afterwards.
The drum beat could be a bit more interesting, and you could increase the volume of the guitar to make it more recognisable. After all, you say you're centred on guitar riffs..
The outro was nice, and provided a fitting end to it.
[Review Request Club]