Sometimes I get this urge to map lore onto rules like it's a puzzle, and for me the clearest split is between the competitive 'rules-as-gameplay' side and the narrative/RPG side. If you want the God-Emperor shown as an unreachable, omnipotent force that shapes entire armies without ever stepping onto the board, then most editions of 'Warhammer 40,000' (matched play) do that brilliantly — and frustratingly. The tabletop rules treat him like an institution: doctrines, relics, psychic auras and faction traits that bend the game around the Imperium without actually letting you play him as a five-foot-tall stompy hero. I love that because it keeps the mythic scale intact; the Emperor is the background gravity, the reason armies fight and priests zealotically chant, rather than a giant statue you move with a measuring tape.
On the other hand, if you want the Emperor as an active, tactical demi-god who once led wars personally, 'The Horus Heresy' rulesets (the 30k-era) capture that era's portrayal better. Playing scenarios or reading the campaign supplements, you feel the Emperor’s strategic presence — whole legions react to his plans, primarchs operate under his shadow, and the rules allow (in narrative forms) for much more direct reflection of his genius. Between club nights and late-night hobby chats I’ve found players who love the 30k feel because it makes the Imperator an actor, not just a throne.