Sure, at the time this movie was pretty well loaded with famous faces, but in terms of aging, maybe these aren't the greatest actors in the world, but it did pretty well. Here's a look at the famous people in Heat:
Robert DeNiro – One his last good movies. Have you ever noticed how DeNiro's not good at acting romantic? Every time he's involved in a love story, it's hard to believe that either a) he actually likes the girl, or b) the girl actually likes him. This is his only blemish as an actor, well, that is aside from the decline of skills over the past couple decades, but that happens to all of us when we age. Another funny thing I noticed about his role in this movie is that it seems like every time he meets someone, he has to tell them his “A guy once told me, "Do not have any attachments, do not have anything in your life you are not willing to walk out on in 30 seconds flat if you spot the heat around the corner.” speech. Poor Tom Sizemore has the look of, "Oh god I hope I don't have to hear that speech again, I just want a beer!"
Al Pacino – This is the closest we ever come to Al Pacino vs. Robert DeNiro in their primes. This too is one of Pacino's last good movies, but he's full blown comedy in this one, so it's hard to say if he's still a good actor. He's absolutely hysterical in this though. He gets funnier as more time passes between viewings of this movie. He should try to be funny more often, or at least embellish the full blown caricature of himself he's become.
Val Kilmer is in this, and he has to hear DeNiro's "leave in 30 minutes" speech. His girlfriend is …
Ashley Judd, whom is quite hot. She doesn't really do anything special in this aside from cheat on Val Kilmer, with none other than …
Hank Azaria, who's surprisingly nice and shady in this. He likes Ashley because, "Cause she's got a... GREAT ASS! And you've got your head... ALL THE WAY UP IT!"
A young Natalie Portman tries to kill herself.
Tom Sizemore, as mentioned above.
Jon Voigt was pretty good in this, but this is well before he started using his time to write queer letters to Barack Obama because he disapproves of his job.
William Fichtner, who may not sound famous, but he was the blind guy from Contact. Most recently, he was "Mob Banker Who Gets Shot" in The Dark Knight. Seriously though, this guy has been in a bunch of stuff. He's kind of like the 90s version of Kevin Bacon.
What's really interesting is you have two early 90s musical performers who no longer were relevant musically, so they turned to acting, and that's Tone Loc and Henry Rollins, which leads to the question, who has had a greater impact on pop culture between those two? I say Tone Loc because more people know "Wild Thing" and "Funky Cold Medina" than anything Rollins has done, however, many of my generation loved Rollins little stand up comedy act or "spoken word" if you will, so it may be a push.
Dennis Haysbert is in this as well. If you don't know him as President Palmer from "24", I'm sure you definitely know him for pimping All-State insurance nowadays.
Perhaps one of the most pleasant surprises is you get Jeremy Piven playing a mob doctor in a brief role. It's not a cameo because he's not famous enough, so it's just a great instance of someone landing a role in a movie before they were famous, though I'm sure some may argue that Jeremy Piven still isn't famous, but c'mon. He makes "Entourage" or at least did when that show was good for a couple seasons.
Lastly, Deniro's girlfriend in this looks kinda like Julia Roberts, to the point I swear they wanted her for the role, but she turned them down. Whoever that chick was, she was never really in anything else that big, but for one movie, she got to pretend she was having sex with one of the greatest actors of his time, so good for her.