The 4th Generation generated a lot of developement of the metagame, particularly in the the lead position. Ultimately if you used a poor lead or had a poor matchup you lost momentum and could in theory lose you the match. Some PKMN were banned because of their lead potential; they could reliably set up a situation or stop another situation from setting up. Violation of the Support Characteristic was a big reason why Deoxys-S and Froslass were both banned from their respective tiers, despite their fragile nature. Gen 4 also saw a big battle between "suicide leads", "attacking leads" and "bulky leads", each setting a different pace. Commonly support leads set up Stealth Rock, although others included Dual Screens, Trick, Sleep, Rain Dance, Baton Pass. Some Pokémon even had several lead options - the current Gen 4 Azelf analysis has potentially 6 lead sets out of 8 sets over 2 tiers.
Gen 5 continued this trend of strong leads, if anything made them better. With Sturdy acting as a free Focus Sash, bulky leads such as Skarmory, Forretress and the new Crustle can lay down at least Stealth Rock and maybe even Spikes. The update to Mental Herb means Deoxys-S can once again terrorize leads and out Taunt many others, including Speed ties with Focus Sash holding brethren. Against this, Mischievous Heart is also a problem with support leads, as Thundurus and Whimsicott can out Taunt many other leads, including Aerodactyl and Deoxys-S, two of the fastest Pokémon in the game. Some new set up moves potentially sweep teams - Shell Smash Cloyster and Quiver Dance Volcarona are both incredibly threatening and are quick ways to stat up. Lets not forget the weather starters, Tyranitar, Hippowdon, Abomasnow and now Politoed and Ninetales, each can provide an entire genre of team by themselves.
To balance this up Game Freak introduced a new mechanic - it is often thrown around that the new Team Preview has ruined the concept of a dedicated lead. By running a dedicated lead, the opponent could just switch in something that counters / fares well against it, like using Choice Scarf Scizor against your Azelf lead - do you attack, set up Stealth Rock or switch out? But you could do likewise, and sub out your dedicated lead to fair better against their "anti-lead" - but then that leaves your dedicated lead as dead weight later on.
However, what Gen 5 does let you do is "bluff" your lead. Despite Team Preview, it is possible to choose 6 different Pokémon, each of which can use a formidable lead set. By confusing the opponent, you can still run your dedicated lead and the opponent will be forced to guess what you're going to lead with.
What I hope this generation will tend towards is a series of versatile leads - Pokémon that do well both in and out of the lead position, effectively offering the player with 2 or 3 different leading options. In turn this gives you better versatility and can suit the lead depending on what team you are facing. There were examples of versatile leads in Gen 4 - Swampert and Hippowdon were good examples, but there are less wallish kinds too. The Gen 4 standard Lead Dragonite using Draco Meteor / Extreme Speed / Superpower / Fire Blast functions as both an offensive lead and good mixed attacker early / mid game. Offensive Trick users like Starmie, Jirachi and Metagross have great early, mid and late game potential destroy walls with prediction or revenge kill threats.
So, I ask you - are leads now obselete? Or with the offensive nature of Black and White is the lead as important as ever?
leads are just an old 4th gen vocab word that no longer exists in 5th gen. you cant say one pokemon is your lead since all 6 pokemon could be your lead. there is simply no point for the word lead to exist in 5th gen anymore unless you are leading the pace of the game or something.
basically get out of the 4th gen mentality and adapt to 5th gen
Thats not really adding to the discussion - in the end you have to start aka lead a game with something. What do you do when you see an opposing team - Do you try to counter what you think they're going to lead with? Or do you try to set up something of your own? Do you build leading into your team? Do you use a scout? Or do you just wing it and hope for the best?
Personally, whenever possible I try to lead with my rocker. Early rocks are a huge deal still. That said, if it looks like a bad idea, of course I lead with something else. Whoever beats more of their team, a weather starter, whatever I think starts my game off right.