Whether DRM was one of the main reasons for Crysis' lackluster sales, I don't know (I have no idea what kind of "SecuROM" DRM it had). I've passed it for now due to its high system requirements, but I will probably buy it at some point from a sale for a couple of bucks. Or even more, if it appeared in GOG, DRM-free of course. :)
Crysis 1 didn't have DRM in the online sense. It had a disc-based variant of SecuROM. It sold poorly initially because it required hardware far beyond what most people had at the time, which is commercial suicide. Funnily enough, its sales picked up a few years later when the average hardware caught up.
Crysis Warhead used online SecuROM. Crysis 2 used Origin as DRM, except the Steam version, which used Steam natively.
The interesting thing was that Crysis 2, unlike number 1, ran perfectly fine on average hardware of the day. It sold reasonably on consoles, but sold ridiculously poorly on PC (digital and retail combined, going on the basis of retail figures and Steam peak usage figures).