I think you're choices of how you view it are:
- it is his proper name that sounds silly in English
- Shinra Sr. is referred to as プレジデント (purejidento) and Rufus as 社長 (shachou) as a means of distinguishing them during the dialogue so you know which Shinra is being mentioned
Although even the Japanese fans on the wiki aren't sure about it, I would go more for the latter for the following reasons:
- President Shinra is never referred to as 社長
He is only ever called プレジデント in game, and never given the respectful title 社長*. That no one would use that to refer to him but instead just use his first name seems strange given his powerful position in the world. (Other external books have used 社長 when talking about him.)
- Characters use プレジデント alone
Were プレジデント his first name, this line of dialogue would be kind of rude coming from Reeve:
リーブ
「プレジデント！ 本当にやるのですか？ たかが数人の組織をつぶすのに……」 (Reeve: President! Are you really going to do it? Just to destroy a group with few members...)
Compare this with later scenes when Rufus is in charge, the senior staff don't refer to him using his first name alone:
ハイデッカー
「ルーファウス社長のご好意だ！ きもに命じとけ！」 (Heidegger: Courtesy of Rufus-
shachou! Don't forget about this!)
スカーレット
「社長……なんだかイヤ～な予感がするわ」 (Scarlett:
Shachou... I have a bad feeling about this)
ハイデッカー
「社長！ 処刑の準備がととのいました」 (Heidegger:
Shachou! Preparations for the execution are finished)
ハイデッカー　「わからねえ。社長と連絡がとれない！」 (Heidegger: We don't know. We can't contact the
shachou)
リーブ　「社長やない！ シスター・レイのほうや！」 (Reeve: Not the
shachou! The Sister Ray!)
Other characters also use respectful terms when talking about Rufus using his name:
【兵士Ｄ】
「ルーファウス様、到着です！ 準備完了です！」 (Rufus-
sama has arrived! The preparations are complete!!)
シエラ
「新社長のルーファウスさんがここへいらっしゃるそうなんです。艦長は朝からそわそわしてますわ」 (Shera: They say the new
shachou Rufus-
san is coming here. The captain has been restless since the morning)
シエラ
「ルーファウス社長が来たのは宇宙開発を再開するためなのでしょうか？」 (Shera: I wonder if the reason Rufus-
shachou is visiting is to restart the space program?)
He is given a title showing respect when his name is used. No one does that when they mention President Shinra.
You can also see this contrast in Tseng's dialogue, where he says the same thing about each Shinra. For President Shinra:
ツォン
「ずいぶんと長い時間がかかったが やっとプレジデントに報告できる」 (Tseng: It has taken quite a long time, but I can finally
report to [the] President.)
And when Rufus takes command:
ツォン
「……どうかな。とにかく社長に報告だ」 (Tseng: .... I wonder. Anyway, we will
report to the shachou.)
Unless Tseng was on a first name basis with the late President Shinra, I think that points more towards 'President' being a title rather than a name.
The one time that might contradict this is when Cloud sees President Shinra in the mako reactor:
クラウド
「ひさしぶりだな、プレジデント」 (It's been a while, President)
クラウド
「待て、プレジデント！」 (Wait, President!)
Cloud doesn't refer to Rufus using any kind of respectful title (I think the only time anyone is AVALANCHE does is during the Junon scenes when Aerith disguised as a Shinra troop says "Rufus...
sama" once), and he isn't using polite language here (～だな instead of ～ですね
. But in this context he is talking to his former boss. Even if he isn't being completely polite, he might still be using his formal title.
