Is it necessary to recite a formulated "sinner's prayer" to get saved?
ABSOLUTELY.....................NOT!!! The bible says we are saved by grace through faith in Christ, and the Greek word for faith is defined as "to trust in, to rely upon, to adhere to". So based on that, it is not necessary. If one recites some version of it and mean what they say, then yes, it will be a tool to save them. The "sinners prayer" is a tool, but it is not necessary. Every time in the New Testament when a person said a prayer at the moment of their salvation, it was spontaneous and never formulated. Many cases people did not say a prayer when they were saved, it simply says they had faith or believed. "Believed" by the Greek words and context would be defined in the bible as having trust and not just intellectual assent to the facts.
Also I do not like some versions of the "sinner's prayer" I have read. Some seem to weave a doctrine of something other than salvation by grace through faith, they muddy that up, and thus are un-biblical in their doctrines.
It is also not necessary to use altar calls, although it is not a sin to use them either. It is a sin to make people think they cannot be saved if they don't walk up to the front during the altar call.
We are saved by grace through faith, but we do earn rewards in heaven by good works. There will be a judgment of rewards separate from the determination of who goes to heaven or hell. Repenting of sins can also avert God's judgments in THIS life for believers.
With recent prophecies I heard of the churches needing to repent of some things, I am inclined to prefer not to do everything exactly as it has been done in some churches just to make a point.
This can also explain why some people in churches that do not use the "sinner's prayer" seem to be genuinely saved, rather than merely outwardly religious but not having been spiritually regenerated inside, it is that they have faith and trust in Christ, but many may have barely even heard about the "sinner's prayer". It is far worse to recite a version of the "sinner's prayer" that contains a false gospel, rattle it off mindlessly thinking it will magically save you just because you recited it, and not said any prayer from the heart, than it is to never recite a prayer to get saved, but to trust the Lord for your salvation. I will tell you that many people in denominations who don't use the "sinner's prayer" are truly saved.
With so many Evangelical churches becoming emergent (Apostate), I doubt if many people entering them are truly getting saved. It is possible because of salvation by grace to remain saved and become apostate, you will enter heaven, but have no extra rewards to your credit. I think the Holy Spirit in me is literally not letting me shut up about how the churches need to repent. People who read this should talk to people they know in church circles. Spread the word. I am not kidding, I think I have the Holy Spirit on this right now. Spread the word far and wide. If they don't listen, let them know God wants the people to re-organize in whatever ways they can after the fire of God's judgment passes through the churches. Being saved by grace through faith, membership or attendance in an established church is entirely optional.