I beat the pennant mode, which requires 80 wins to accomplish. Luckily, you don't have to play all 132 games of the series, as the manual calls it, as once you win your 80th game, it plays a neverending celebration sequence. You have to either shut off or reset the console to end the scene.
There is so much wrong with the game, mostly due to what the fielders do, regardless of the situation. Setting that aside for now, some basic things that should be in any baseball game by this point are missing. I could look past these if it was a game from the previous console generation. Some of the general issues are:
In pennant mode, you are ALWAYS the home team.
The only choice you have in your starting lineup is the pitcher.
There is no DH, which is a minor issue for me.
Players can't play out of position, so if you decide to pinch hit a lot in one game, you can end up having the same bench player playing multiple positions as well as batting multiple times in the lineup.
I was expecting something special for hitting a grand slam, given the name of the game, but nope, just the standard home run sequence.
The CPU AI is awful. It will always try to throw out the lead runner. Even if the CF picked up the ball at the wall and the runner is one step away from home plate, the CF will try to get the out at the plate. You can use this to your advantage on a single to advance the hitter to 2B if there's a lead runner at 3rd, as the CPU also doesn't know how to handle a pickle, with the fielders anchoring themselves to the base and simply throwing to the other base when the runner reaches a specific distance from the base and no other fielders helping out unless their programmed location to go to happens to cross paths with the pickle.
Grounders down the line that are slightly foul have a low chance of being called fair.
The only fly ball that can be foul is one that's fouled back behind home.
There were a few times where it glitched and the fielder would not throw the ball. I got a couple "infield HRs" due to this, as the infielder simply stood there with the ball as all my runners ran around the bases. It happened once when I was in the field, and I was wondering why my fielder wouldn't throw the ball.
It doesn't seem like the game recognizes a force play at home plate, as all force outs there required tagging the runner from what I can remember.
A foul tip the C catches counts as an out, even with less than 2 strikes.
According to the manual, in a 2-player game, only player 1 can call time, meaning player 2 is reliant on player 1 calling time in order to make a subsitution.
Pitching
There are no curveballs, sinkers, etc. It's just fast, normal, or slow pitch, and then you choose the location. There is a tiring mechanic, where the pitcher will stop being able to get as much "movement" on the pitch. For example, he won't be able to get the pitch to go as far inside. I will give the game credit for including this. There are no passed balls or wild pitches. There is no such thing as a high ball -- as long as it's over the plate, it's a strike. Only a high pitch will hit the batter. For certain pitchers, a specific pitch and location in the stike zone will never be hit, so once you recognize this, you'll be able to strike out every batter on three pitches -- at least until your pitcher tires if it's at the start of his appearance.
Hitting
You can swing low, middle, or high; as well as inside, middle, or outside. As far as I can tell, high swings will NEVER connect. If you want to hit a high pitch, swing middle and it'll connect if your timing is on. The CPU is extremely easy to figure out as to where the pitch will go, as it took me all of one game to figure out that whatever direction the pitcher moves on the rubber is the opposite of where the pitch location will be, i.e. if he moves right on the rubber, he'll pitch to the left side of the plate (this is true probably around 95% of the time). You can also bunt, but once the pitcher starts his delivery, you can't cancel the bunt, and it will be a strike if you don't connect, as the concept of offering at a pitch isn't here. You also cannot connect with a high pitch, which means if you're playing against a human and s/he squares to bunt, pitch high for an automatic strike. The CPU never bunted, so after playing an entire "season", I think I'm safe in assuming the CPU will never bunt.
Baserunning
The manual states the "base runners will automatically advance only when there is a baserunner on the base before them." This is false. As soon as the batter connects with the pitch, all baserunners will take off. If you're used to playing competent baseball games, it'll probably take you a while, if ever, to get used to automatically sending your runners back on a popup. It's almost impossible to steal, except for home due to taking advantage of the atrocious CPU AI. Attempting a hit and run is pointless, as if you send the runner early and the batter connects, the runner gets teleported back to where he would have been if he didn't start running early. The runners start to slide extremely early and the slide takes forever to arrive at the base. The runner seems to have to reach the "far" side of the base, e.g. the 3rd base side of 2nd base, to count as reaching the base, making many instances of it looking like the runner is obviously safe but ends up actually being out.
Fielding
The game will automatically field for you, but you can override it at any time, with the auto-fielding taking over again if you stop moving the fielder yourself. This is a definite plus. That's about the extent of the positives in this aspect. The fielders move extremely slowly while ball is in the air, meaning a high pop-up on the infield has a good chance of dropping in. There are no bad bounces. There is a specific location on the bag that counts as actually touching the base -- I had a couple time where I ran right over the bag and it didn't register as a force out, with the first time causing me to lose out on turning a double play as my SS ran right over 2B and I just assumed it was a force out before throwing to 1B for what should have been the 2nd out of the DP. There were many, many times that there was a high fly ball to the outfield, almost always to CF, and the fielder camped under it missed it. The biggest problem with fielding is that the fielders all have a set location to go to, regardless of the situation. A couple examples:
If the bases are empty and there's a grounder between SS and 3B, those fielders are set to cover 2B and 3B, so they will both avoid fielding the ball, even if its trajectory is 2 steps to the right of the 3B or left of the SS.
For some reason, the outfielders seem to be programmed to backup a base on the infield, so on a hit between the CF and RF, the CF and LF will run into the infield to cover a base leaving the RF all alone to cover the entire outfield. This means that on those hits that reach the fence and to the right of where the wall is horizontal as seen on screen, it'll bounce off the wall in the direction of LF and the RF will have to chase the ball halfway across the outfield.
Unless you have someone to play against, avoid this game. Even at $6, I feel like I overpaid. It might be good for multiplayer, but there is at least one better option on NES -- Baseball Stars is the only other NES baseball game I've played for more than an hour, and it's much better than this.