Please don't let me get into an argument about the definition of genocide, Gunfighter. I won't sleep for weeks.
As for something you pointed out - smallpox blankets - yes, those were absolutely the earliest forms of biological warfare that we're aware of today, and yes, the distribution of the blankets to the natives, who obviously hadn't built up countless generations' worth of "immunity" to smallpox and greatpox (syphilis), was quite intentional. One of my professors discussed this very ordeal in a class earlier this semester and quoted one of the masterminds behind the use of the blankets to effectively poison entire tribes at a time, and it's very clear that he knew what was going on. Moreover, if one of the two remaining living smallpox samples in the world (one at CDC in Atlanta, one in Russia) happened to get out, it would probably kill about 70-90% of the population born after the smallpox virus was officially eradicated, because that's when vaccination ended. With that in mind, it's pretty safe to say that something like 70-90% of the natives that contracted smallpox, probably closer to the latter, died, and that's only the one disease. There are, as has been mentioned, dozens of other European diseases that killed the natives too, and it's no surprise that so many died.
Because it was well known that the natives would die as a result of smallpox, because it was well known around Europe that both smallpox and syphilis were usually either scarring for life or deadly, and because the distributors of the smallpox blankets knew exactly what they were doing, yeah, I would certainly call European expansionism and imperialism a genocide, just as I would call those that died under slavery victims of genocide - it's no secret that whipping a man, starving him, and torturing him will kill him sooner or later.