Of all the games I've tried the best part of leveling up has always been the AA points, talent points, perk points type bit. Having a choice how to grow your char is just more fun than the stuff you get automatically from your class. It's partly wanting to have an avatar that's exactly how you want them plus also it adds a strategy game element in trying to judge what will work best. So my perfect game would have to be skill based however levels are such a simple and straightforward mechanic I'd have a hybrid system. There'd be levels but when you levelled you got a skill point to use in one of the skill trees.
Currently i'm thinking along the lines of something like max level 50 with therefore each character having 50 skill points and the proportions being something roughly like:
Warrior tree, 30-40 skills, some of these being simple improvements e.g dodge1, dodge2 etc set out in in tiers.
Scout tree, 20ish, outdoorsy stuff
Rogue tree, 20ish, indoorsy theifly stuff
Priest trees, 12-20ish, different trees for different Gods
Wizards, lots of different magic schools with 6-12 spells/skills each
General tree, unknown number of odds and ends like first aid
Crafting, multiple trees, 6-12 skills for each craft
Specializing would have benefits as the skills would be in tiers and you'd need to have
spent a lot of points in a tree to unlock some of the most powerful skills but being a
jack of all trades would be an interesting and tempting option and certain hybrids
would be natural e.g ranger would be a mixture of the scout and warrior trees. You'd
want it so every time a player levelled up it took them ages to decide what to train in
because there were so many possibilities.
I also like the idea of class being more like faction i.e if you joined a particular temple as a guard then that would be your temporary class / faction in a way because as you levelled you'd pick your skills from the ones available from your faction's trainers. If it was a dwarf blacksmithing type temple/God for example that favoured heavy armour, hammers and shields then those would be the sort of skills you could learn there. If it was the Royal Scouts then the list of available skills would include things like bows, tracking and light axes.
Also you'd have elite sub-factions so I wouldn't have a Paladin class I'd have a
particular temple that had Paladins. You could join the faction as a guard but could
only join the Paladin sub-faction of the temple if you met their requirements e.g 20
warrior skills and a big quest showing dedication to that temple. Joining the Paladins
of that temple would unlock the option of choosing certain elite skills and spells when
you next levelled up. Ranger would be an elite sub-faction of the Royal Scouts faction
with some elite options to choose from but require maybe 12 skill points spent on the
scout tree and 12 points in the warrior tree plus a big quest. Apart from the unlocked
skill and quest options becoming a Ranger or Paladin would be more like a title change
as you went from "Stormhammer Temple Guard" to "Stormhammer Paladin".
I'd want crafting skills to use up some of your total skills so it would be a hard choice that would only appeal to crafter type players. On the other hand not so many skill points that you couldn't be a master blacksmith who was still a decent fighter or an jeweller-enchanter who knew a enough magic to go and fight stuff when they were in the mood. They could never be as tough as players that specialized completely in fighting / magic but they'd be ok.