First things first: it has nothing to do with Eric Draven. He's a revenant, a ghost given flesh in order to extract revenge. No, the real reason for "Crowlander" is Top Dollar. Sure, he's a charismatic psychopath who rules a criminal empire, but I maintain he's also an immortal.
Exhibit 1: A Closet Full of Swords
Knives? Sure, he's a villain. One sword? Why not, he's filthy rich, he can be eccentric. But an entire armory of swords? Easily accessible? That he's clearly practiced with?

There's also the fact that this man, who clearly must have enemies both in the police and organized crime, doesn't carry a sidearm. In fact, he has to borrow one from his bodyguard.
Okay, yes, by itself this isn't convincing. Moving on...
Exhibit 2: Intelligent Anti-Immortal Tactics
All right, so in the previous example Top Dollar hears from a trusted lieutenant and a groveling flunky that there's a guy out there who gets shot/jumps out of windows/etc and keeps on trucking in his quest for vengeance, and this doesn't faze him in the least. He doesn't question the apparent insanity of it all. He just goes "Hmm, that's interesting."
So when he arranges things to have Draven's last person on the "to-kill" list in the room with him, he also arranges to be surrounded by dozens of armed goons. This is good strategy, because as we've learned from the Highlander films and TV show, immortals can be killed conventionally -- they just don't stay dead. So obviously his plan is for his goons to shoot Draven, whereupon Top Dollar can take his rival's head easily.
Except that he's surprised when Draven shows up, because he doesn't get that characteristic "buzz" immortals get when they meet each other. So he thinks that, maybe, this guy is just a loon hopped up on drugs.
And then he is totally gobsmacked when it turns out his opponent is immortal after all.
Also: a katana shows up in this fight scene. Because when I think of "Immortal Scottish warriors," I think of ancient samurai swords.
Exhibit 3: Running to Holy Ground
Because that's what you do when you're immortal and you don't want to fight another one. Why else would this incredibly rich, incredibly dangerous man hide in an old abandoned cathedral?
Also, kindly note how neither his bodyguard nor his sister are all freaked out by this. "He has power you can take," she says, and T.D. replies with "I like him already." Even as he's running for his life, Top Dollar is planning how best to take Draven's Quickening.
Exhibit 4: Swordfighting in a Lightning Storm
Some of you may be asking, "What about the proscription against fighting on holy ground?" Well, first, that prohibition is only between immortals. So when T.D. has his assassin take a shot at Draven's totem bird, that's allowable. And when that results in Draven losing his powers, Top Dollar now knows for certain that he isn't fighting another immortal... and therefore the rules don't apply.
If you're a fan of the series, you know that electricity is a metaphor for the Quickening, so it's no surprise that the final battle of the movie takes place where there is lots and lots of it about. Oh, and look, Top Dollar uses another katana.
Conclusion: Top Dollar is an Immortal
The only question this begs is, "What happened to him afterwards, since his head wasn't taken?" To my mind, there are two possibilities.
One possibility is that his hired goons in the police department -- come on, if you're an immortal crimelord you're going to have some cops in your pocket -- pulled him out of the morgue and falsified the burial data. After this he probably spent the rest of his life hiding from ghost-men before another immortal (probably Duncan) took his head.
Another is that the supernatural vengeance of Draven ("Thirty hours of pain. All at once! All for you!") was able to short-circuit immortal healing, leaving Top Dollar permanently brain-dead, if not dead-dead.
Either way: he was totally an immortal in that movie.