I am watching Phantasm 3 right now. It's the first time I have ever seen 3, but I have been a big fan of the first two movies for years. I kind of quit after 2 because I figured there was no way a budget horror series could stay good that long. 3 is pretty decent so far.
The first movie is pretty dated, but still effective. Much like Evil Dead 2, for whatever it matters, the first sequel is basically a remake of the first movie. Also like Evil Dead, Phantasm fall squarely into the "Random Shit Happens Without Real Explanation" genre, but it plays it off very well. Rather than being confused by what's going on, we understand the skeleton of the plot: The tall man is using dead bodies to make servants for some transdimensional shit. If it were explained any more, I am sure it would just be cheesy and lame.
Angus Scrimm (of TV Guide and Alias fame) is damned excellent as the Tall Man, too. Although clearly staying on the serious side of horror, the movies never seem to take themselves all that seriously. There's always a nice air of low budgetness around the flicks, and I think the movies would feel pretty damned hokey if that weren't so.
Phantasm -- much like Reanimator, another series much better than anything Raimi could even dream of.