Indeed due to Shia Muslims, Shuraa' (consultation) is acceptable only when no explicit command of Allah and his directly chosen Caliphs are available and it was not the case ever for selecting the successors of the apostle of Allah --peace be upon him and his household-- due to Qadeer Sermon and many other Ahadeeth recorded from him. However even if Shuraa' was usable in this case then Ijmaa3 of the Muslims was required for that to become religiously approved, and an Ijmaa3 that does not contain Imam Ali --peace be upon him-- (who is among the Ahlul Bayt and recognized as being infallible in [33:33]) and even contain his opposition for about 6 months is doubtful to be religiously approved. Even Umar himself has confessed in [Bukhari, book 82, hadith 817] that the selection of Abu Bakr was a sudden action that got established afterwards. He adds then, in the same reference, that "No doubt, it was like that, but Allah saved (the people) from its evil". However, contrary to what Umar had claimed here Shia Muslims do not believe Allah has saved all Muslims from that Evil, but only due to the long and deep patience of Imam Ali --peace be upon him-- He has only saved some of the Muslims who remained with him. Such is Shia belief anyway, I know Sunni brothers would not easily admit it ;) Shi'ism instead very much believe in this Hadeeth from Bukhari that says: Narrated Abu Huraira: Allah's Apostle said, "Whoever obeys me, obeys Allah, and whoever disobeys me, disobeys Allah, and whoever obeys the ruler I appoint, obeys me, and whoever disobeys him, disobeys me." [Bukhari, Volume 9, Book 89, Number 251] which explicitly talks about the prophet --peace be upon him and his household-- determining some rulers! One may discuss if by this ruler it is meant the successor of the holy prophet --peace be upon him-- or a ruler for some city in the Islam land of those days when the holy prophet --peace be upon him and his household-- was still among the Muslims, or maybe the substitute of him in Medina when he was going outside for a war or else? However, even if the second and third probability are taken into consideration and the former case is not mentioned still one should ask from himself how can it be possible that a wise man who send chosen men as his appointed rulers to the other cities to rule them based on Islam, or never leave Midina unless has substituted an appointed ruler in his place, now leave his people all around the Islamic land with no appointed ruler to rule over them? If having a ruler, any good or bad ruler (see some Sunni authentic Ahadeeth about it here), can be sufficient then why to appoint some preferred one for his time and then stressing on the point that "whoever obeys the ruler I appoint, obeys me, and whoever disobeys him, disobeys me"? What a bad ruler orders to would be then equal to the rules that the apostle of Allah --the pattern in Islam-- would order? No such a ruler should be a distinguished one and the holy prophet --peace be upon him and his household-- could not be indifferent about such an important issue that can turn the whole way of Islam after him, a religion that is to remain intact to the end of times. Certainly he has introduced the two weighty things (ثقلین) to tell us something even if the Sunni scholars would not agree upon a large portion of the context of the Qadeer Sermon. Why Ahlul Bayt are such stranger to Sunni brothers now that they know very little about them and barely use their Ahadeeth and description of Qur'aan? No we believe some 12 appointed ruler were introduced by the holy prophet --peace be upon him and his family-- in name so that the Muslims will not astray after him.
However, also note that each of the four caliphates after the holy prophet --peace be upon him and his household-- was selected in a different way, Abu Bakr was chosen by a small group of Muslims not all of them being among the highest ranked Muslims or as caring and compassionate about Islam as was e.g. Imam Ali --peace be upon him. Some people like Imam Ali --peace be upon him-- even never gave the pledge of allegiance to Abubakr before 6 months after the holy prophet --peace be upon him and his household-- had passed away, that is not before the holiness Fatima --peace be upon her-- passed away. / Also Umar was not chosen by any consultation, but directly appointed by Abu Bakr, like Abu Bakr was more caring about Islam after him compared to the holy prophet --peace be upon him-- that he didn't appoint any successor after him? / Uthman but was chosen in a very strange way, Umar set up a group of 6 persons only for them to decide whom will be the next Caliph only from within themselves, and Uthman was chosen among them eventually. / Imam Ali --peace be upon him-- might be the only one who was chosen as the next Caliph by the Ijmaa' of Muslims, people coming to him from any direction almost forcing him to accept becoming Caliph. Although according to Shia belief he had been already chosen by Allah and His apostle previously.