Praise be to Allah.
In order to understand this issue we must note that there are two types of reward, the reward for knowledge and the reward for accompanying the Prophet (peace and blessings of Allaah be upon him). Some later members of the ummah may do deeds that are greater in reward than similar actions on the part of some of the Sahaabah because they will have no one to support and help them, and because they will be subject to a great deal of temptation, but they will not have the reward of having accompanied the Prophet (peace and blessings of Allaah be upon him) and met him.
Al-Haafiz Ibn Hajar said:
The hadeeth “The righteous among them will have the reward of fifty of you” does not mean that people other than the Sahaabah are superior to the Sahaabah, because simply having more reward does not prove that one is superior.
Moreover, the difference in reward is with regard to the same type of deed. But the superiority attained by one who saw the Prophet (peace and blessings of Allaah be upon him) cannot be matched by anyone.
This is how we may interpret the ahaadeeth quoted above.
Fath al-Baari, 7/7
Shaykh al-Islam (Ibn Taymiyah – may Allaah have mercy on him) said:
They – meaning the later members of the ummah – may have good deeds equivalent to those of fifty men among the Sahaabah, of the deeds that they did at that time. That is because the Sahaabah had help and support in that, whereas those who come later may not have help and support. But the fact that the reward will be multiplied for them in cases where it is not multiplied for the Sahaabah does not mean that they are better than the Sahaabah or that their virtue is any greater than that of the Sahaabah. What the Sahaabah achieved in terms of faith, jihad and fighting the people of this earth by supporting the Messenger, believing what he said and obeying his teachings before his call spread, his word prevailed, the number of his supporters increased and the proof of his Prophethood became widely known, indeed when the believers were so few in number and the disbelievers and hypocrites were so many, and the believers spent their wealth for the sake of Allaah, seeking His pleasure in that situation, is something that no one can achieve the like of any more. As it says in al-Saheehayn, the Prophet (peace and blessings of Allaah be upon him) said: “Do not curse the Sahaabah, for by the One in Whose hand is my soul, if any one of you spent the equivalent of Mount Uhud in gold, he would not attain the level of any one of them, or even come half way.”
Majmoo’ al-Fataawa, 13/65, 66
Moreover, there is no virtuous deed that those who come later can do, but those who came before did something similar in a more perfect fashion.
With regard to the words “They will have the reward of fifty of you because you have supporters who help you to do good and they will not have any supporters who will help them to do good,” this is correct in a case where a deed done by a single person among those who come later are like the deed done by a group of people among those who came before, so he will have the reward of fifty. But you should not imagine that one of those who come later will do deeds like those of some of the major Sahaabah such as Abu Bakr and ‘Umar, for there will never again be a Prophet like Muhammad (peace and blessings of Allaah be upon him) with whom people may do deeds like those that were done with Muhammad (peace and blessings of Allaah be upon him).
With regard to the words, “My ummah is like the rain, I do not know whether the first of it is better or the last of it,” although this hadeeth is not very sound, what it means is that among those who come later there will be those who are similar to those who came before, and they will be so close that the one who tries to compare them will not know which is better, even though one of them is in fact better.
This is glad tidings for those who come later, that among them will be those who are close to those who came before them, as it says in another hadeeth: “The best of my ummah are the first and the last, and between them there will be some crookedness. Would that I could see my brethren.” They said, “Are we not your brethren?” He said, “You are my companions.” This shows that precedence was given to the Sahaabah, because they alone are his companions, which is a higher status than merely being brothers.”
Majmoo’ al-Fataawa, 11/370, 371
It is worth pointing out that there is no basis for the phrase used in the question, “the best of generations is my generation”, although it is often used in the books of Ahl al-Sunnah. Moreover, there is a mistake with regard to its meaning. If this is what he said, then he would have said after it, “then the one that follows it.” But the wording of the hadeeth is “then those who follow them.” The wording of the saheeh hadeeth is: “The best of mankind/people is my generation” and “The best of my ummah is my generation.”
And Allaah knows best.