Baseball Stars improves on everything its predecessor offered and more.
So why a 9.0, instead of a perfect 10? My only complaint is that in the original Baseball Stars for the NES there was the ability to customize team stats, trade players, but this feature has been removed from both the original Neo Geo version of Baseball Stars and in the sequel.
This, however, does not take away from any of the fun factor in this game. Immediately when you boot up Baseball Stars 2, everything seems quicker, in your face, flashier, pretty and all around more fun. Gone are the slow base runners of the first game. Instead every time there is a hit, the batters run quickly to the bases, and have a small animations showing them running, as well as for close calls, and getting out (It's always fun to see your players screaming at the umpire IMO).
That doesn't mean all batters are fast. Some are so slow that they could hit a ball to right field and still be out on first.
Batting is no longer as hard as it was in the first, in terms of getting on base because of the speed. Also, a new feature is the power up hit, where one's player receives an enormous bat made for making home runs. You're limited to the amount you can use in a game so it never feels out of balance and becomes a point of strategy on when to use them. A good way to stop someone form using their power up is to bean them, but that can cause a charge to the mound, where a fight breaks out, and your pitcher immediately becomes fatigued. Fatigued pitchers throw slowly, and curve balls are near impossible. So there's some give and take on when to hit someone in the face with a fastball.
Another new feature is the ability to adjust difficulty. I've always thought the learning curb to win a match in the original was always too difficult. Here you can set it to easy difficulty or hard difficulty. Easy will take a few tries to get a victory if you're poopy at sports games, while hard does offer a challenge like the first game.
Winning matches results in trading your players away at the end of a match and some extra cash. I wish there was a time when you could always make trades instead of at the end of matches. Another really cool feature that I like is between every change, the game saves. I know this doesn't seem like a big deal, but it makes picking up wherever you left off great, since you never really feel bummed out that you have to play a team from the start (lest you're doing awful and need a restart).
When you lose in single player your team's owner is pissed off and complains why you lost. Getting yelled at is never fun in real life but to see some Anime-esque dude getting pissed about the great American past time somehow works. Even if you win the manager will still have a recent to criticize, but he's the jerk and you're the player. I guess that's the life of a baseball star.
In closing, Baseball Stars 2 is great by yourself or with friends and is essential to any Neo Geo collection. The price for the game isn't too steep in terms of AES these days (expect to pay about $100, unless a great deal comes up). It's addictive, simple, not too over the top, but quarky enough to make you always wanting to come back for more.