If you're looking for a good PSP basketball game, pass on this one and wait for something better to come along.
NBA offers basic exhibition and season modes. Also included are three mini games, which include the Playstation Skills Challenge, a mode called Paint in which you compete against the CPU to capture different areas of the court by making a shot from that area, each worth a different point value, and a three point shootout. If you're accustomed to basketball games on home consoles, you'll notice that there is no franchise mode, and no unlockables, if you're into that sort of thing. These omissions aren't a big deal, but should be noted.
Surprisingly, the graphics look good, and technically, the game is sound. Courts have the appropriate team logos and colors, and have a shine to them. Rotating billboards change on the sides of the arena. The player models are better than you'd expect. Occasionally, before and after shots, the game will pause for closeups of the players. Stars get an Upper Deck trading card complete with signature when attempting a shot, and for all players, a more generic close up shot appears after a made shot. There is no play by play commentary, but in addition to the ball bouncing, you'll hear sneakers squeaking, dunk attempts, swishes, crowd reaction, and the music that plays after a shot is made. The arena announcer will announce out of bounds calls and fouls. Two camera views are available, a sideline and a follow camera.
As for the gameplay itself, on offense, you can perform spin moves with the triangle and and square buttons, and pump fakes with the circle button in conjunction with the R button, which serves as a modifier. The L button allows for icon passing. Notably, there is no turbo button. The D-pad calls plays on offense and defense, but these seem to have no effect. Alley oops can be attempted as well, with the modifier button and pass.
The game has a unique shooting mechanism, which involves pressing the shoot button twice, once to start the shot, and once again to release it. A colored halo surrounding the ball indicates the shot quality, red meaning bad, yellow being ok, and green being perfect. If you time a shot perfectly, a cha-ching sound will let you know. However, this shooting mechanism presents a problem with layups, as it's harder to time your shots closer to the basket, and you'll end up missing more layups than you'd like. Fortunately, dunks only require one button press. With some practice, you'll get used to when you should press the shoot button a second time and not rely on watching the halo color.
Unfortunately, the gameplay in NBA suffers severely from numerous oddities present in the game. The most prevalent problem is that there are too many blocked shots. Any jump shot you take standing face to face with a defender is just about guaranteed to be swatted away. Even your seven foot centers will have this happen too frequently. Even more unrealistic is that blocked shots pretty much result in the ball going out of bounds, just like in the most NBA Live 2004. You'll learn quickly that moving your ball handler around quickly will shake his defender and allow him to take a shot that won't be blocked. Another effective scoring technique is to use your teammates as screens to get open.
The game also has some very bad AI. You'll notice many unforced CPU errors, such as stepping out of bounds, or shooting inappropriate three point shots from way out, or going for a two point shot at the end of the game when down by three. I even experienced a frustrating situation in which I was up by three at the end of the game, and the CPU decided to go for a two point shot close to the basket. However, my CPU controlled player inexplicably fouled the CPU opponent, resulting in a three point play that sent the game into overtime. Like so many other basketball games, your teammates seem uninterested in fast break situations and will leisurely jog down the court, when they should be sprinting instead.
Too many other problems plague this game to make it enjoyable. The play calling is useless. Shooting free throws is a matter of luck more than anything. The frequency of air balls is far greater than in any other basketball game. So is the frequency and ease of jump shots taken from behind the backboard, which go over it and in more often than not. On inbounds plays after turnovers, the CPU will often fail to set up, and you can get an uncontested layup easily. Upon completing a season and winning the NBA championship, there is absolutely no indication you've accomplished anything, not even a message, and the playoff bracket doesn't even indicate the NBA Finals winner.
NBA shows some potential, and could be a good game with some more work, but as it is, it's almost unplayable. If you're looking for a good PSP basketball game, pass on this one and wait for something better to come along.