Blood Money is a right killer...
The gameplay is impressive, allowing you to choose from a range of different methods to achieve your Hit and if you do pull of that perfect Hit, it gives you a sense of satisfaction than just to going in with all guns blazing. The graphics while nice are no more than that so there is still a big improvement to be made in that area and I hope they will with the improvements in Direct X 9 and the brand new Direct X 10.
Another major factor is the game has a big replay value allowing you to play over and over without getting bored since you can try to complete the missions in various ways for a challenge.
My only gripe with the game is that it could of had a few more levels or bonus missions, the AI can be pretty stupid and needs improving and I would love to see some kind of on-line play considered for future games but a nice story and improved game mechanics makes this the best game in the series.