Gen 2: Curse is one of the things that made Snorlax the single most dominant OU of all time. Curse+Rest is an amazing combination, increasing its below-average defense stat and making it one of the best walls in the game, while hitting extremely hard with Curse boosted Double-Edges and Returns. Its presence is so huge, phazers like Tyranitar, Skarmory, and Steelix are used mainly for their phazing moves to deny Snorlax. After a Curse, there are very few Pokemon that can OHKO or even 2HKO Snorlax, one of them being Machamp, who can only do so before a Curse, and whos super effective Cross Chop has shaky 80% accuracy and only 8 PP. CurseLax's gen 2 OU analysis
Behold, the single most dominant Pokemon in any OU tier in history. Snorlax combines power and resilience with deadly unpredictability, a set of traits that lands it a spot on virtually all serious teams. Its presence defines the GSC metagame, all but forcing teams to play one or more sturdy Normal-resistant Pokemon while simultaneously killing off the viability of manifold special attackers with its enormous HP and sky-high Special Defense. Snorlax is a constant threat to offensive teams as a Curse sweeper, a team sweeping machine as a Belly Drum user, a relentless battering ram as a mixed attacker, and a reliable wall as a RestTalk user. However, it isn't completely unstoppable. Snorlax's Defense stat is on the low side, meaning that despite its massive HP stat, Explosion from common OU Pokemon like Cloyster and Exeggutor is enough to take it out with minimal prior damage. It will usually be forced to use Rest if it gets poisoned, giving the opposing team a reprieve that they can use to gain an advantage. Defensive teams will nearly always have Skarmory for Snorlax and usually pair it with a semi-reliable counter to mixed Snorlax as well, which can sometimes leave Snorlax unable to do any meaningful damage by itself. However, make no mistake: these constitute but minor flaws among Snorlax's array of overwhelmingly powerful attributes.
Gen 3: An improved Physical movepool with Shadow Ball, Brick Break, and Focus Punch while testing out some Hidden Powers it hadn't used before, like Bug and Ghost (remember, this was before the Physical-Special split) was a major buff. However, along with those came EVs and Natures, which made Physical attacks even more powerful. That, along with Metagross and Salamence being the clear #1s in the OU town along with Sub+Focus Punch running around made Snorlax slightly less scary than in gen 2. ResTalk mechanincs also changed slightly, which sucked for Snorlax. Despite all this Snorlax was still a major OU, despite having competition from Regice and Blissey as a special wall. Oh yeah, curse was still a mainstay, being mandatory on the most popular 'Lax set
Snorlax is a special wall with a great defensive and offensive presence thanks to its Curse set as well as its access to Self-Destruct, as taking out an extra opposing Pokemon or a sweeper that wants to overpower it can be crucial for a game. While it does have some weaknesses, namely mediocre Defense, low Speed, and a vulnerability to Spikes and sand, its strong points make it the force that defines ADV OU.
Curse Snorlax can be a secondary check for special attackers such as Zapdos because it is usually buffeted by Sandstorm and doesn't have a reliable way to restore its HP. If Curse Snorlax is the last Pokemon on your team, there will be a strong possibility that you can make a comeback, as Snorlax can boost up and beat down phazers such as Skarmory, Suicune, and the rare Steelix, which can no longer use Whirlwind or Roar against it.
Gen 4: The Physical-Special split was good news for Snorlax. It could now rampage with Curse boosted physical Elemental Punches, and it also got several new tools in Zen Headbutt, Iron Head, Seed Bomb, Superpower, and even Gunk Shot to toy with. It also got Outrage to damage Dragons (although Ice Punch was usually better). However, unfortunately, Fighting type moves were now more powerful than Brick Break, and more consistent than Focus Punch, meaning that Infernape and Machamp were trouble, and Life Orb was now a thing. However, Curse was still a great option, and Snorlax could still use it to great effect. Curse on Snorlax is still set in stone, and Curse Snorlax still has a large presence within the DPP OU metagame. Snorlax's Gen 4 OU analysis:
He's big, he's round, he's bulky, and he's back. Snorlax is among an elite group of Pokemon that have been OU for all four generations. Unfortunately for Snorlax, DPP has been the least favorable of them all towards him. With countless new offensive Pokemon added to the mix and items such as Life Orb boosting their damage output, Snorlax has a very difficult time keeping up. In addition to this, Snorlax's typing always has and always will leave a lot to be desired. With a STAB that is resisted by over one-third of the metagame, it's tough to see why you'd want to use Snorlax at all.
>Despite the nearly crippling faults mentioned above, Snorlax has a niche unlike any other Pokemon. He is the most durable offensively-inclined special tank in the metagame. This unique niche allows Snorlax to come into many of the special attackers in the metagame with near-impunity and have his way with them. While Snorlax isn't going to be winning any Best Pokemon awards with his faults, because of his assets, it's hard to deny him his rightful place in OU amongst the big boys.
What do you get when you combine rock-bottom Speed with high Attack and immense special bulk? You get the ideal Pokemon for a Curse set. Snorlax practically defined the use of Curse for sweeping in previous generations, and still carries the mantle admirably through DPP. The problem with Curse Snorlax these days is that everything else is so immensely powerful that even Snorlax's bulk isn't enough to save him from being ravaged. That aside, Curse Snorlax is still an immense threat and can set up against a surprisingly large chunk of the metagame.
Hope this helps!