I find it quite unlikely. I noticed that most of the 3GS and below models started to disappear a year or two after the iPhone 4 came out, as Retina was a massive upgrade to phones. On the other hand you can find a significant number of people still hanging on to their iPhone 4/4S, which is pretty amazing when you realize that these phones are already 3-4 years old.
Anyway I'm one of those people who clung onto the iPhone 4 and only decided to change this year. While it has served me well, it's really beginning to show it's age and it struggles to run many applications. iOS is laggy, many websites on Safari are extremely laggy, Google maps is laggy when navigating the maps, applications take a long time to load and often crash due to lack of memory or unresponsiveness.
And you have to consider that the iPhone 4 is miles faster than the original iPhone, just like how the iPhone 6 is miles faster than the iPhone 4. Given that my iPhone 4 struggled quite a it in day-to-day usage, it's a pretty fair assumption that the iPhone 2G would struggle far more.
The iPhone 2G was also designed with a very different intention in mind. Back then, most people didn't subscribe for data plans yet. It was meant to be a phone that was capable of doing occasional web-surfing and checking of email. The way people used their iPhone 2Gs were very different from the way that people use their iPhone 6 today.
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I remember when I got the 3GS, it was still probably the happiest day of my life. I thought that phone was absolutely lightening fast and the design was gorgeous. The 3GS could easily still hang with some of the phones on the market today and I still think its a great looking phone!
But yeah, I'm sure the iPhone 1 is probably a really slow machine, I would be curious to see someone chime in who still uses it daily!
I felt bad for the 3GS owners when the iPhone 4 was announced. It was like, bam, every single phone just became obsolete overnight. Every phone screen looked like utter crap and looked completely outdated after I saw the beauty of a retina screen.