Yeah, you’re absolutely right.
I could see a workable movie based on Manic Miner.
Starring Danny DeVito.
Yeah, give him a goatee and a crowbar, and I think it could work pretty good! 
I actually have to agree with this, but I’m mostly going from his performance on ER. I just think he could nail the character, as I see him: quiet desperation, dry humor, iron-willed determination, and that certain bit of nerdiness.
Chirs Walken is like who I’d cast for G-Man, but he’s, I don’t know, too Christopher Walken. It’s like Kelsey Grammer playing Beast; yeah, he’s got the right characteristics, but he’s a little too known, a little too much of a star. I’d want someone who could kind of disappear into the role.
Of course, with big-budget movie-making money to through around, maybe the thing to do is completely CGI G-Man and use the original voice-actor. It would just make him that much more surreal (my theory is G-Man is some sort of cosmic entity that contracts out to various organizations and factions for his own reasons, and uses agents like Gordon as his tools).
The actor I see playing Gordon Freeman is Edward Norton, though Christian Bale would be an acceptable substitute.
I give you the Half-Life youtube movie trailer! Not bad, for what it is… …
Edward Norton I could see; he’d make an equally good Barney (dunno if this idea has been done to death yet or not). Christian Bale I don’t quite see as Gordon Freeman, but the man does have excellent range.
Re: Joust, has it occured to anyone that ostriches don’t actually fly?
I’m sure they’ll handwave it away in the film by calling it, “falling with style.” 