I loved the first one back when it came out. I played maybe 3 or 4 missions of the campaign and never bothered with it. I had followed the game since the demo, and the real fun came with making your own missions. There was just so much mucking around you could do in the game world, since the developers had made everything available to you. Me and a friend used to put invincibility on and strap like 100 satchel packs to a Jeep and see how high we could launch it. Then the devs made it possible for us to mod the game properly and I ran a modding website for about a year with my own creations. After the first expansion came out in 2002 I got bored with it. That's a whole year of obsessive OFP playing. Not bad for 1 game.
This was all possible because of the sheer openness of the game, allowing the player to do what they want in it rather than just playing preset missions. I really hope that Codemasters intend for OFP2 to be like OFP1 in this sense.