CoD1 and 2 were on the PC, it was CoD3 that was consoles only, XBox 360 and Wii for sure, dunno about PS2/3. I played CoD3 on XBox a bit, it was actually alright.
I've never played CoD1, so I can't really comment on it, but I've seen a lot of frag movies from it. It does look like a much more PC orientated game (I think I'm right in saying it was PC only?). There is much more recoil, for one thing.
CoD2 is when consoles started infecting the game. Guns like the PPsh and the Trench Gun spoiled the game a bit. Add the fact that any long-range class (Scoped or non-scoped single-shot rifle) gets 3xFrag, then it's a bit spammy. I've played a few competitive scrims, and I can say after playing CoD4 competitively it was a nice refreshment. A lot less focus on holding down mouse 1 at your target, not having to worry about recoil. The one-shot rifles dominated the game. There were longer-range encounters, so SMGs were kinda outclassed, unlike in CoD4, where you can run around with your 74u and dominate the server. The Thompson SMG was quite hard to handle, if you just held the trigger you would soon be aiming at the sky. Compared to CoD4 or 5 or 6, it's a lot... 'better', if PC orientated is your cup of tea. The lack of sprint made me rage, I would always be hitting shift, and end up meleeing thin air.
In conclusion CoD2 is definitely worth a buy. CoD1 I can't comment on, but I've heard a lot of good things about it. I wouldn't buy it if you were just a casual gamer, but if competitive is more your scene, then I'd recommend it.