I've played many games and read the rules for even more than that. I enjoy doing rules comparisons even if I don't play the games and as I've gotten older I've become an advocate for simpler rules more and more. Nothing too simple, mind you. I don't want the sort of game where everyone just says they are doing something and the GM says, "flip a coin" and that determines everything. Although I've seen some humor games that work on that principle and they do have their charms, I must admit. One area of simplification that caught my attention some time ago was the Swords and Wizardry (OSR Retroclone of D&D) method of having a single saving throw for each class rather than multiple categorical saves. It works by having each class and race receive a bonus to certain types of saves rather than having a chart of different types of saves. For example the magic-user class receives a +2 bonus to saves against spells, including spells from wands, staves, etc. His actual saving throw does not change, just his chance of success.
The key to this is the secret of d20 systems, which is a secret anyone can figure out and many of you probably already have, but I will state it anyway so we are all on the same page: every +1 bonus equals 5%. That's it.
When combined with the 1 and 20 rule of d20 it all falls into place. The 1 and 20 rule, of course, sets the absolute maximum chance of success or failure at 95%. No matter how many bonuses you stack up or how many penalties you are forced to accept you will never have anything less than a 5% chance of success or failure. Your system is, effectively, closed. Open systems where you can simply keep adding bonus after bonus, plus after plus, are abhorrent to me. It is one of the main reasons I loathe Pathfinder. It's all too complicated. Classes exist because many of the qualities that make a person a wizard are the same for all wizards, like the casting of spells and the lack of armor. They aren't there to prevent you from making the character you want with all the special bells and whistles. If given the freedom to do what they want people tend to copy something else anyway. All potential wizards will focus on the things that make a successful wizard at the expense of the things that make something else. Like a fighter. All a class does is codify and standardize those things for you. Keep it simple and keep it fun, I say.
Let us take a quick look at comparison. You have a S&W Magic-User at 1st level. The saves for such a character, using the old multiple category method are:
Death Ray/Poison: 13
Wands (all): 14
Turned to Stone: 13
Dragon's Breath: 16
Spells and Staffs: 15
So our M-U needs to roll 15 or better on 1d20 to succeed in a save against spells. That's a 30% chance of success.
In the standard S&W single saving throw system, however, the 1st level M-U has a Saving Throw of 15. This is the same as his normal save for Spells, better than his Dragon Breath save (a dex/stamina based save) and worse for the others by 5%-10%. However, using this single save method the M-U gets a +2 bonus (10%) to all spells including spells from wands and staffs. So now his 15 is actually 13 for spells and staffs (10% better than the multiple category version) and 5% better against wands (15-2=13 vs 14). The trade-off for this is to be worse at Death Ray/Poison and Stone by 10%. It evens out across the board. By comparison the Cleric gets a +2 to Paralyze and Poison specifically, both of which require fortitude and willpower to overcome.
Your D&D 3.X and Pathfinder editions brought the saves down to 3 types: Fortitude, Reflexes, and Willpower, which they felt covered all bases. What it did was fuck wizards who tending to lack high stats in Constitution (buffed FORT), Dexterity (buffed REF) and Wisdom (buffed WILL) found themselves once again paying an over-inflated price for the ability to make a feeble light for 10 minutes once per day. Essentially the ability to recognize a magical spell and use that knowledge of magic to help counter it through a saving throw (the previously employed Save vs Spells) no longer counted for shit. Well done WOTC. Dicks.
5th edition now has 6 saving throws, each keyed to an ability. So instead of making an old school save you are, effectively, making an Ability Check. There is some virtue to that, I think. If for no other reason than it gives the abilities some meaning in terms of saving throws, but again a good DM would already take that into account when the situation warranted it. It also removes the Ability Check as its own method of conflict resolution by making it the saving throw, essentially. Against whatever DC is set by the DM or the action itself.
Now my argument is FOR a single saving throw system. Using the S&W system the lowest any class's saving throw value will get is 4 (for Fighters and their ilk). All the non-warrior classes (Magic Users, Clerics, Thieves, etc.) will go down to 5 and stay there. At a saving throw of 4 you can only fail on 1, 2 or 3 (that's a 15% chance of failure) and on a 5 you fail on 1-4 (so 20%) and you always have your bonuses. Using the multiple saves system a Magic User at level 16 would have a 3 for his save against Spells. With a +2 bonus for the single save system he effectively has a 3. On the other hand that same M-U would have an 8 against Dragon Breath under the multiple saves system and no bonuses. Under single save he has a 5, which is 15% better. Yes, mathematically it benefits the players more to have a single saving throw and it is also easier on the bookkeeping. It also means that a fighter, who never gets better against spells than 8 on the multiple saves system gets to face them at a 4 on the single save system. And all the classes get this good score much sooner. Is that too easy?
Not as far as I am concerned as this is an OSR system and therefore deadly in so many ways that a modern system is not. The old school mentality does not hold with giving a player multiple chances to not die simply by rolling a magic d20 and ignoring whatever happened. It expects the player to be smart about play, in its anthropomorphic way. It does, however, mean that the player automatically knows his save in any situation. It is up to the player to apply that class bonus and remember it, but that should not be too big of a chore since the categories are rather small. It also speeds up play and keeps the players playing instead of consulting charts all night. Ultimately this is ideal, this playing instead of looking up the rules constantly and having to make 5 rolls for every action.