While 1440p seems to be touted as the starting point for decent VR, I've tried it with three separate 1080p phones and I think it works fine. I'm not scrutinizing the image for pixels, waiting to jump out of my seat and scream, "J'accuse!" Maybe that makes the difference. I wouldn't say 1080p makes for world class VR viewing, but there is nothing wrong with it for a budding enthusiast. I will say the SD 820 SoC and 3.5GB (effective) RAM helps more than the other two devices I tried. Both were Android, an Idol 4 (SD 617, 3GB RAM) with dedicated VR headset and an Idol 3 (SD 615, 2GB RAM) with a one size fits any phone generic headset.
The Idol 3 was probably the lowest spec I would venture into VR with. In fact that is exactly what I did. The Idol 4 I tested at a store... The 5.2" screen isn't ideal. 5.5" seems to be a better starting point.
I also believe that despite what the pundits say about the Alcatel headsets not being equal to a Galaxy Gear VR or Google Daydream, they are definitely better than a generic for securely cradling the handset, fit, comfort, preventing light bleed and field of view. At least vs the generic I tried which was a $30 item and not the cheapest one i could find.
I definitely feel the Idol 4S Windows VR package is value added, for those so inclined, and if the Idol 5S has a Windows itteration I hope the VR trend continues. Microsoft seems to be putting a lot of eggs into the AR (Augmented Reality) basket and I would not be surprised to see things taking off in that direction for Mobile and Headsets very soon...