X4 has too small of stages and gives you life back at halfway. But, it does have two playable characters, something that is way important. Also has probably the best Sigma.
But you can't dismiss X2. I mean, just watch the speedrun. It has godly mechanics, perfect level design, the music is really well done, has two different endings with a possibility of 4 different boss fights possible, the boss fights are some of the most clever in total (crystal snail is the most fun boss fight ever with weakness), doesn't require repeating stages (again, level design). Mid air dash is so awesome, and, most importantly, the controls in X2 are literally the definition of perfection.
X3? The game is the biggest ********* ever with the layout of the game mixed with Zero. And the ridearmor sections are incredibly forced and don't add anything. I do not like this game to the level I enjoy most other mega man x games. The game also features NES level slowdown and the controls are not as tight as in X2, or even as close.
X5...it's really fun to find everything and the sigma levels are ****ING hard. But come now, this game is rehash done right, but feels like the same game X4 did.
X6 is rehash done with a 5 dollar budget and 3 months to develop. They used the same 5 enemys through out the game, the same lazy backgrounds and was just a disappointment. I remember getting this on christmas and playing it for about 10 minutes before putting the game down, running upstairs and crying. It was Megaman 7 all over again, and I haven't been able to sleep right since. The game has NIGHTMARE for a reason.
Why do you guys care about a story? wtf? Have you played a mega man game before?
I agree with the fact that X2's final sigma fight being really bad, but the 2nd form of sigma is really good.
X is clearly the 2nd best of the X series. Controls. Graphics. Music. Design. Bosses. Techskill. Impossible speed run spots.
X2/X/X4/X3/X5/X6