This is a very good question Umby! From generation to generation, what qualifies as stall will usually differ. I'll just touch a bit on RBY and DPP I guess...
I'm not exactly sure to what extent stall is viable in RBY. There's neither clerics nor entry hazards. Stall options could be quite limited to good Rest users and maybe some Pokemon that can set up to increase Defense and/or Special. I personally don't think stall is very viable in RBY with crits everywhere and make every Pokemon much less durable. Being slower also means a higher chance of getting a critical hit. By trying to stall out the opponent, you're putting yourself at huge risk of a critical hit or even worse, a freeze. I've never seen / used a stall team in RBY though so I might be wrong somewhere. RBY is a rather fast metagame that isn't really suited for stall :/
DPP might be the best generation for stall (or maybe GSC or ADV >.>). It has a good balance of entry hazards, Rapid Spin users, clerics, walls, spinblockers, and oppositely an equal counterpart of offensive Pokemon so that neither stall nor offense will overpower each other. But what is considered stall in DPP is often blurred by misconceptions etc. Stall teams would usually consist of the aforementioned things minus maybe the offensive Pokemon bar a failsafe such as Choice Scarf Tyranitar / Rotom-W. With 'semi-stall' and bulky offense around, some might mix them up with a full stall team. Good stall teams are incredibly great of the ladder at the certain period of time it was made for. Stall teams aim to counter the most common and relevant threats on the ladder but not to counter every single threat out there as that is also unrealistic. Stall teams often do not have any form of offense bar their failsafe and maybe Pokemon that have naturally good attacking stats such as Hippowdon and Gyarados.
Stall teams are self-sustainable and aim to outplay and outlast the opposing team with smart play and good use of the Pokemon. Entry hazards and phazing go along hand in hand to rack up plenty of residual damage to the opponents while they struggle to do anything back to you while you fall back on your sturdy walls that can even heal off any damage taken and just repeat the phazing cycle until the opponent is severely weakened. Through cores and sole stall Pokemon, stall teams counter the common threats and work towards wearing down the opponent till the extend that the stall teams gain a win condition.
Stall isn't just about trying to survive longer than the opponent, though that's what you have to do to win every battle anyway. It also does damage slowly but gradually to opposing teams, often through residual damage in the form of entry hazards or status. There's also weather stall, mainly hail since sandstorm is used as an anti-weather as opposed to using it as an element of stall. Hail is a great and fast way to wear down Pokemon without Leftovers as Ice-types are quite rare in DPP OU.
Stall is one of the most irritating playstyles to face, and probably one of the harder and more consistent playstyle that is well-suited for ladder play. I don't think stall is as common in Tournaments though I've never really participated in one :d On another note, it can be quite fustrating to be randomly accused of using stall when you definitely aren't and you're just walling your opponent instead of stalling them though there's much similarity. Stall can and will do something back and walling might just be as good as forcing something out without doing anything / attacking back. Stall = wall but wall =/= stall or something like that.
I think this is a very insightful thread to what qualifies as stall and what doesn't. Also please try to avoid talking about BW as RoA is for past gens discussion though making comparisons to BW is fine >.> sorry if I'm overstepping anything :d
Member of the GP Team- VM for a check / stamp!