With regard to the multiplayer - while it can be played as a DM twitch fest, the core gameplay is all about strategy. Getting the power weapons, getting to the best ground, and defending your position from others. A good example is Snowbound, one of the maps in the beta. With tight corridors under the surface, the shotgun is located in between the two major spawn zones and is a key power weapon in controlling that zone. Adding to this are the addition of shield walls, in which delicate games of cat and mouse take place as players stare each other down through weapon-impenetrable walls of energy, each one looking to find the upper hand in either a strong short range weapon to quickly take down the opponent (the shotgun) or a clever ruse to draw the shotgun wielding player out of his protective caves into the stinging barbs of a spike grenade carefully placed on the wall by the retreating figure. Or perhaps, another player flanks the shotgun-wielder from behind and disposes of him. Additions like the shield doors may be subtle, but they have a dramatic effect on the general ebb and flow of a map.
With regard to the golden triangle - guns, grenades, and melee, we have another subtle addition to the formula. Sure the golden triangle is still there in full effect, but the addition of equipment allows a period of respite - giving players a chance to recover and plan their next move.
The crucial problem with games like Rainbow Six, which I love and adore, is that they usually devolve into camp fests because, tactically, it makes sense. Unfortunately, dealing with a camper is not very much fun. On the other hand, it can be played on a very high level with members of teams specializing their roles and moving together to accomplish the objective, be it via the assistance of a radar jammer or a pack of C4 on a door covered by hostiles. Halo seems to keep balance well, always giving players a chance to fight back and win in pretty much any situation, whereas if you're outnumbered or ill-equipped in R6 you are, frankly, screwed. They are different types of play entirely, and I enjoy both completely.