Well, I've already stated some reasons above, but to go more in-depth, Blood 2 simply doesn't have the lovably malicious spirit that the original had. The weapons got nerfed
hard in between games, and the napalm cannon that was so useful for burning zombies in 1 is completely underwhelming in 2, to the point that there's really no use in using it.
Some enemies explode violently when they die, but you're given no warning that it's going to happen, and would have no idea to stay away from them until after you've already gotten blasted at least once. The most powerful weapons in the game have barely any ammo laying around for you to find. Some enemies take way too long to kill, and the satisfaction you get of destroying the opposition in 1 is lost in 2 where you realize you're better off just running past everything. Small enemies called Bone Leeches attack you by jumping on your face, and the manual that comes with the game never says how you're supposed to get them off, leaving you to die wondering what you did wrong.
In Blood 1, everything was made with 2D sprites, allowing more detailed and grisly death animations for enemies that get blown up. In Blood 2, the engine is a very early 3D engine, meaning that environments are mostly undetailed, most enemies look the same, and they all generally die the same, too--either just falling over or blowing up into undetailed chunks.
The antagonists are almost completely nonthreatening, especially by comparison to the creepy abominations you had to fight in 1. While Blood 1 didn't have the hardest final boss, Blood 2's final boss is downright pathetic by comparison. Blood 1's final boss is a giant skeletal minotaur that could kill you simply by looking at you. Blood 2's final boss is an immobile, nondescript blob with an eyeball sticking out. Gee, I wonder what its weak spot is?
And last, but not least, Caleb himself. You see this picture of him here? You see how he looks like a combination of my avatar and the Disturbed mascot?
This is a character that is supposed to be threatening. Vicious. Almost feral. In Blood 1, he sings "Ring Around the Rosie" while in a city that just came under a firebombing attack. He kills indiscriminately, whether it be his true enemies or just innocent people who get in the way. He throws dynamite at zombies and cackles when they explode into chunky kibbles. His favorite weapon is dual-wielding flare guns, which obviously burns up anyone who gets hit by one. He goes to a carnival and looks for any excuse possible to kill the mimes he finds there, and when he sees an attraction for JoJo, one of the carnival employees, he appears to forget why he's there in the first place and chants "I want JoJo! I want JoJo!" When he kills Cerberus, a two-headed dog monster, he says, "Good doggy. Play dead." In short, he's a sadistic, intimidating force of nature.
In Blood 2, though...he is easily outsmarted over and over again by the new (and very wussy) big bad, gets caught in multiple train crashes, whimpers "Make the hurting stop" whenever he gets attacked, and upon being told that he has the fate of the world on his hands, his reaction, rather than being "How exciting!" is more like "I don't care."
You starting to get the picture here?
