MegaMan X4 is a great game with unique gameplay, awesome music and lots of replay value on its PS1 debut.
+ Total revamp of the graphics
Graphics mean nothing to games as far as I am concerned, though at the time that this game was released, the PS1 graphics were on top with the N64 followed right behind. So to see X go from 16-bit cartoon animation to rich, detailed 32-bit visuals would've left gamers in awe at the strength that the PS1 had. From the waterfalls to the snow covered bases to the jet-ride chase scene with a particular boss, everything stands out on its own.
+ Double gameplay
At the start, one can choose either X or Zero to beat the game with each protagonist playing a lot different from the other. X has his usual run, shoot and jump aspect from the SNES games along with locating armor upgrades and obtaining the weapons of the fallen bosses. Zero on the other hand is a different story. He no longer has his arm buster and attacks with a light-saber, making boss fights a tad bit more difficult. Add the fact that Zero has no armor upgrades which means he takes more damage than X and relies on "abilities" than actual weapons gives his playthrough a bit of a unique edge over X. If you were familiar to MegaMan and Bass, this game would definitely be familiar with MegaMan X4.
+ Great soundtrack
The MegaMan franchise have been known for a lot of things, the soundtracks being one of them. If you are a fan of pop (Japanese pop at that), you'll immediately fall in love with the music. Or even if you are not a fan of Japanese pop, there is a guaranteed track that will hook you in.
+ Tight and responsive controls
The one thing that makes or breaks a game is its control scheme. Needless to say, the controls for X4 are just as tight and responsive as the X-games from the SNES. Along with button configuration makes other commands like dashing a lot easier to reach.
- Horrible voice acting for anime cutscenes
It is very common to see anime in English with absolutely dreadful voice acting. The cutscenes in X4 are no different and are guaranteed to make you wrench at how bad they are. Sure they are better than the voice acting in MegaMan 8, but not by much.
- No difference between X and Zero's paths
As different as X and Zero are gameplay wise, there is little to no difference to how the game ends or the paths that they take. While the characters they encounter are different in character and strive, there is absolutely no difference between the 2. If Capcom had gone the "Resident Evil 2" way and have separate scenarios on the way the game ended, then it would not have been so bad in the long run.
+ - Difficulty might be a bit of a turnoff
MegaMan games have always been known for being difficult to beat and X4 is no different. While the game is a bit "easier" with X with the armor upgrades and all, it is a tad bit more difficult with Zero seeing as how he cannot attack from a distance and sustain a ton of damage from enemies and bosses. But in all reality, with enough practice the game becomes a breeze in the park, especially the final boss.
All in all, MegaMan X4 is still a great addition to the X-series as a whole with its unique gameplay, awesome music and challenge to keep you coming back for more and more, though the lack of difference between X and Zero's paths are a bit annoying. If you love platformers or MegaMan as a whole, play this game. Or buy the MegaMan X Collection for the PS2. You can't go wrong with that bargain.