End of Days gets a bad rap, but I think a great deal of this is due to its initial premise. It's extremely 'cool' to be anti-religion these days, so big-budget movies with a core religious theme tend to get unnecessarily slammed. I'm not religious myself, but I do often enjoy supernatural and religiously themed stories, due to the themes and issues they frequently explore. So its success all hinges on whether you can accept a plot guided by supernatural religious elements or not. If you can, and you enjoy action movies occasionally, you'll probably enjoy End of Days.
Arnold plays a depressed ex-cop turned high-level body guard with a suitably tragic back-story. Some people will enjoy his performance, others won't. Again, it depends on how you come to this. If you are expecting a versatile actor who changes personality with every performance, then you won't enjoy it. If you like Arnold, because he is exactly what he is, Arnold, then you'll probably have a ball. After all, who ever hired Charlton Heston or Humphrey Bogart or Christopher Walken to play a part in any way other than the specific way they do? You don't hire such actors because of their chameleon-like acting abilities, you hire them because their sheer screen presence is such that they stand out from the crowd and you enjoy seeing THEM in the role. As such, you either relish those actors in their parts, or you you dismiss them as wooden or bland. It depends on the viewer.
The director, Peter Hyams (2010, Outland, Timecop, The Relic), has a tendency to enjoy very dark cinematography, and in this case it suits things perfectly. There are lots of scenes lit primarily by flames or torchlight, that set the tone. Meanwhile, John Debney's (Cutthroat Island, Passion of the Christ) score is also one of his best, and probably one the most effective 'demonic' soundtracks since Goldsmith's Omen trilogy. I would be remiss not to mention the effects work as well. Having watched the DVD special features, I was extremely impressed with how much old-style artistry and craftsmanship went into many of the effects. There was a great deal of miniature work involved, which is too often sidelined for less effective CGI these days. End of Days used a careful blend, only really using CGI where necessary.
End of Days is a great roller-coaster ride of a movie, entirely suited to the date it was made for, and has a surprising amount of depth. Under the action and excitement, it's really a story about the main character's redemption, finding himself again, and discovering a meaning to his life after all he thought he had lost. It's also a classic good versus evil tale. To top it all off, we get a surprisingly touching and moving finale, which perhaps left a lot of people on too much of a downer, yet I found it the perfect conclusion to the story.
All in all, End of Days is either a love-it or hate-it movie. It's not perfect, but I thought it was an excellent film, and one of Arnold's most interesting characters. If you don't mind religious themes, enjoy larger-than-life characters and adrenaline pounding action, then chances are you'll have a fantastic ride.