MDK 2 has aged incredibly well. It was awesome in 2000 and still is today. It's really much fun and full of funny ideas. For me one of the best games ever. Some are whining that it's difficult or frustrating. It really isn't too hard, trust me. I'm not an expert player and I had no problems to beat this game. You can save your progress everytime you want. Sometimes you need a bit time to figure out how to beat a boss, but what's wrong with that. Three totally different playable characters and all of them are much fun.
In my opinon, the first Hitman is much better than the four sequels and the very best one here on GOG. From the second game onwards, the series had the mini-map, which kind of ruined the gameplay, because you always knew where your target was. The first one is more realistic and has a perfect balance between dark humor and seriousness. The hotel level is my favorite, it's a huge sandbox where you can just do funny stuff and kidding around. Forget Hitman Contracts, which is just a bad console remake of the first game.