There are tons of slider sets in here. I would say about 90% are really good. They all focus on a few different things and improve them. No slider set is perfect and you probably will have to tweak them in order to have them match your gameplay.
While some of their opening posts might come off as "preachy", the ones below all have dedicated guys behind them and do tons of testing. (Apologies if your slider set isn't listed, most likely just an oversight)
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Charter04's Sliders
All Madden
Great sliders if you are looking to set up quick and play. Not very hard to implement and you don't have to follow any house rules (personally I like no house rules)
http://www.operationsports.com/forum...n-sliders.html
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JoshC1977's Sliders
All Pro
A bit harder to implement since you have to change things outside franchise menu and within, but not that much. Settings are really close to default All-Pro. So if you are more of an All-Madden player it might be too easy.
His first post has the most likes out of any slider thread. Maybe not the best indicator of popularity, but plenty of people enjoy his. So if you play more all-pro then this is up your alley.
http://www.operationsports.com/forum...7-sliders.html
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Flazko's Sliders
All Pro
If you're looking for All Pro sliders and you didn't like Josh's. Try Flazko's. Now these ones will take longer to set up and all the colors and font sizes do get confusing. So be sure to take it one step at a time.
The benefit of these is if Josh's that are mostly default All-Pro don't suit you, Flazko uses more unusual/extreme settings that will change gameplay up. He also has tiered sliders so if it's too easy or hard you can easily change, which is really helpful.
Flazko seems to have the most popular sliders based on posts and view count.
http://www.operationsports.com/forum...dden-17-a.html
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Armor and Sword Sliders
All Pro
Another very popular option if you are looking for a middle ground between Josh and Flazko, Armor and Sword's slides seem to reflect that. You'll have to follow his house rules, but if you're fine doing that then you'll enjoy these. Also plus is they are quick to set up.
http://www.operationsports.com/forum...e-sliders.html
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Jarodd21s Sliders
All-Madden
If you usually kill the cpu on All-Madden and are looking for a real challenge this is the slider set for you. Jarodd also has tiered slider set that is great for helping you find the right diffculty. Also no house rules so no holding back versus the cpu.
Note: Don't start on the black set, I consider myself a good all madden player, but the red set kicks my butt. By far harder than default all-madden.
http://www.operationsports.com/forum...n-sliders.html
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Playmaker's Slider
Pro
Now don't let the pro slider fool you, it isn't exactly pro level diffculty. Based on the slider sets I would guess it is a bit harder than default all-pro but that's talking out of my ***, as I haven't used this set before.
His focus is on animations. The sliders are set out in a way to reduce warping in tackles. Playmaker also uses a parity setting at 100 which is opposite of a majority of the other slider sets.
So if you really don't like the cpu running and tackling animations. This set should help improve that.
http://www.operationsports.com/forum...l-sliders.html
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FistofRage's Sliders
All-Madden
While less known this set focuses on fumbles. There have been complaints on OS about lack of fumbles and the fumble slider not working. Fist's sliders focus on creating more non QB fumbles. Try these if you want more fumbles or need another AllMadden option.
http://www.operationsports.com/forum...n-sliders.html
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whosnext00's Sliders
All Pro
If you really enjoy playing with the speed parity at 100. This is a good all-pro slider set. His focus on preventing suction blocking and getting a good amount of penalties called.
Not too hard to set up and very easy to read. His post also mentions to be wary of small sample size and sometimes you will have crazy games. I think that is a great approach and mindset.
http://www.operationsports.com/forum...explained.html
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MALIBU TAYLOR'S Slider Set
Coach Mode
While the settings are hard to read, this is one of the most popular coach mode sets.
http://www.operationsports.com/forum...de-slider.html
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Cycloniac's Sliders
Cpu vs Cpu / Coach Mode
Another option for cpu vs cpu play is Cycloniac's
http://www.operationsports.com/forum...e-sliders.html
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Last one I must recommend is
TDawg's XP sliders for cfm mode.
http://www.operationsports.com/forum...p-sliders.html
As you can see their are plenty of slider sets for all shapes and sizes. Just remember that A) No slider set is perfect and might have to be tweaked by you. B) Give each set at least 2 games. Don't fall victim to small sample sizes.
I tried to give you a view on the most popular ones in this forum. There are plenty more. If you want to know more about each one, visit the link and ask the people in there. I don't know all the ins and outs of each set.