I don't consider Fahrenheit 451 sci-fi. Dystopian yes, but sci-fi no. It does occur in the future, and it has a few things that require the use of sci-fi elements/setting descriptors that aren't neccessary, but science fiction is not central to the story. I consider A Brave New World sci-fi because without the sci-fi elements, the story wouldn't work. I've never read 1984.
I liked the Gateway series. The whole rationing of resources despite having the resource rich vastness of space within reach didn't make much sense, but I liked it.
This is a list of dystopian fiction I've read. Not a complete list, but it's what I could remember right now --
Illium & Ollympos by Dan Simmons -- Not entirely dystopian depending on location, but a major part of the setting is. This is by far one of my fav book/series ever written.
The Martian Chronicles by Bradbury -- It starts out great, and you watch the decline as you read. The last A few of the stories from The Luggage Store on are just disturbing for how they portray the dystopian future.
The Tripods Trilogy by John Christopher -- Remnants of Humanity fight back against alien invaders. I read this in middle school.
To Live Forever by Jack Vance -- I feel the ending was a copout, but I liked the setting and I admit I did like the main character.
The Dragon Masters by Jack Vance -- I didn't care much for these two stories, but I read them because it was Vance, and I like Vance.
The Last Planet/Star Rangers -- Andre Norton
Desert Called Peace by Tom Kratman -- Heavy on the military action
Patriots and Reach Trilogy by David Drake -- Patriots is seemingly light on the dystopian but it builds and builds driving the characters actions.
The Peace War & Marooned in Realtime by Vernor Vinge -- Bobbling... ruins everything
Starfarers by Poul Anderson -- The dystopian future seems incidental throughout the story, but becomes of prime importance at the end.
Revelation Space series by Alastair Reynolds
Rogue Wizard series by Stasheff. Although each story starts in a version of a dystopian future that varies on how the culture of the planet being visited panned out, it's a mix of elements from both fantasy and sci-fi. They're fun reads. Not great as some other stories, but fun.
Other fiction that is dystopian but not neccessarily sci-fi despite containing sci-fi elements:
Showboat World, Dying Earth(So far in the future the sun is going red giant), The Blue World -- All by Jack Vance, all are in the future and imply sci-fi elements but the sci-fi is not central to the story, or even really used at all.
The Year of the Jackpot by Heinlein -- One of my fav dystopian stories, but not sci-fi.
A State of Disobedience by Tom Kratman -- Modern Military Action, not sci-fi
Empire & Hidden Empire by Orson Scott Card -- Sci-fi elements, but really it's set in modern day. The sci-fi is used as a plot device, but heavily based in modern tech.
The Last Centurion by John Ringo -- Modern Day Military, not sci-fi