Bot ratio is most important when playing co-op. A great deal of co-op maps in both Forgotten Hope 2 & Project Reality alike require more bots to attack than to defend. On Omaha Beach you need to make sure the American team has more bots than the Germans. You can play Omaha Beach with 55 to 60 bots and the Americans can definitely win with the proper ratio. Try playing with 59 bots, put 34 bots + yourself on American team and 25 bots on German team. Skill level between 60 - 65. Spawn time 25 seconds. That's 1.4 to 1 American vs German (including yourself). You can play around with those numbers to see what you find to be the most fun for you.
In real life the Americans attacked Omaha Beach with approx 43,250 infantry while the Germans defended it with approx 7,800 infantry. Not including all the men for armored vehicle crews & such. That's a ratio of 5.5:1, or 5.5 American soldiers for every 1 German soldier.
In many WW2 battles the attacking side had to outnumber the defending side in order to be successful. Of course there are exceptions to that, such as at Brecourt Manor, and I am aware a PC game is not a 1 to 1 equivalent to real life. However it is possible to draw similarities between them. Particularly with games which attempt to implement a certain degree of realism to the extent that a PC game allows for.
Edit: Meant to say sorry if there are grammar mistakes, English is not my first language. If you have any other questions about co-op that I might be able to help with then don't hesitate to let me know