I've never played Far Cry 3 or 4, but I found 1 and 2 at Goodwill, so I will give a brief review.
Far Cry 1 sucked because it was a tech demo released as a game. It looked very pretty in 2004, and they tried to sell it as some stealth FPS, despite it having no stealth mechanics, and sparse health or ammo pickups. Plus a plot cheesy enough that even Uwe Boll improved upon it.
Far Cry 2 was a vast improvement, simply there was a map, and checkpoints, and health and ammo pickups, and partners and a story. Still no stealth mechanics (except for day/night cycles).
Why am I harping so much about "stealth mechanics"? Because these game were billed as some hyper-realistic FPS where you gotta take cover and not run and gun, and you gotta use STEALTH!. However, due to the poorly coded AI in these game the enemy can spot you and start blasting despite what cover or how much you crouch or move slowly. In any good video game with a stealth mechanic, there has to be some visual marker, like the Metal Gear radar with the cones, or the Thief games with the bar, or Skyrim / Oblivion with the eyeball over the crosshair.
Edit: Plus when I bought a new video card 4 years ago it came with a code for a free copy of Far Cry: Blood Dragon but when I tried to redeem it, Ubisoft said it was already claimed. So fuck those pretend French, maple syrup chugging, Canadian bacon butt boy SWPL fucks!