If Harry Potter Was Realistic, Voldemort Would've Won in Goblet of Fire
Every masterplan in fiction, no matter its brilliance, is doomed from the start. It is doomed to be picked apart and criticized by all the true virtuosos of hindsight insights.
Then, the author of the piece is likely blamed for creating the plan only as a plot device and not putting any real effort into thinking it through. The Harry Potter series has been picked apart multiple times and, of course, suffered the same fate.
One of the very special targets for deconstruction is Voldemort's plans; and while some of them are definitely not the brightest (like the basilisk in the Chamber — come on, this is just pointless terrorism), his Triwizard Tournament scheme was outstanding and very thought-through.
And we'll prove that by addressing his goals and means one by one.
Performing the ritual
Obviously, the main goal of the entire plan was performing the ritual and coming back to the world of the living. However, the ritual specifically says that the blood of an enemy must be taken unwillingly, hence — knowingly.
Harry had to know what was going on to be able to hate the idea of it — and he had to be there to die later.
Covering up his return
Voldemort was not planning an immediate assault after being back; instead, he wanted to keep his comeback a secret since, to further proceed with his goals, he had to remain dead in everyone's eyes.
By using the portkey to first teleport Harry to him and then return his body back to Hogwarts, he would've achieved just that while also…
Discrediting the Ministry
The Boy Who Lived dies under the care of the Ministry and Dumbledore.
This news would've severely undermined the morale of the European wizarding community, considering the outlanders would've also seen that.
With the Ministry distrusted and Fudge likely resigned, the chaos and scramble for power would've been perfect for Voldemort.
Keeping his agent
After all that, the one true obstacle between the Dark Lord and the ultimate power would've been Dumbledore. So that's where Crouch-Moody comes into play again.
His second primary goal was bound to be the elimination of Albus Dumbledore, which would've been made easy while undercover and in the midst of chaos.
This plan allowed keeping Crouch Jr. close to Dumbledore and getting rid of the Headmaster.
As you can see, if executed correctly, Voldemort's plan would've led to the perfect scenario: with his powers regained, his followers brought back together, both Harry and Dumbledore dead, and the Ministry and the wizarding society in shambles.
The plan with the Tournament was perfect, but luckily, it was ruined by a few mistakes.