You actually could land in Top Gun? I had the gameboy version and i was only once able to land, i don't even know how i did it...

I think Hydlide for the NES is my number one unbeatable game. Even leveled up fully and with all the items (including the revive) the last boss killed you the instant you fought him.

@D-FENS
I'm proud to say that i've beaten Wizards & Warriors II: Ironsword a few times. Its not so bad. Like most NES games you just have to play it enough to figure out enemy patterns and they become very easy then. But Ghosts & Goblins rocks me still to this day.

Werewolf on NES... Frickin imposible! (For a little boy at least)...
Civilization 4: Beyond the Sword, now THAT'S a hard game (AI is upgraded from standard Civ 4)! Hardest I've played in the genre.

I thought that the landind was just a thing Angry VG nerd did for a laugh. Didn't know it was that hard.

My list:

1. Castlevania Adventure(GB) Simon Belmont was a SLUG in this game. anything beyond level 3 with the moving spikes was beyond me.

2. Seaquest DSV (SNES) The Darwin mission were impossible. Darwin handles like a brick, he dies instantly and you have to flick with him 30+ switches in a maze in minutes.

3. Duke Nukem Zero Hour (N64). I could finish that, but didn't have the patience. I dropped it in the last level after endless respawning. Shame, it was a great game.

4.  Gods (PC)  Could not pass the skull boss. I blame it on the keyboard.

I take pride though on finishing Super Ghouls and Ghosts, Axelay, Jet Force Jemini (Mizar was very hard to beat) and Battletoads in Battlemaniacs.

Wow. This list IS NES heavy. But the game no one has mentioned, much to my amazement, is The Adventures of Bayou Billy. Awesome game, but dang near impossible.

Donkey Kong... those damn Minecart levels!!!

Oh my god, don't get me started on Bayou Billy... That's the one game that taught me how to link together several cursewords in a neat string! God I hated that game, and still do!!!

The knifethrowing sob's were a pain in the proverbial arse... 

F-Zero GX story mode the GP race, still can't beat it

battletoads, NES

There are quite a few hard games that I didn't beat, but as far as games that I spent a decent amount of time on and still didn't beat: TMNT for NES. I tried the game about a year ago(first time in over 15 years) and realized I'd have to dedicate some serious time to beat it.

Mike Tyson's Punch-Out was on this list for a long time, but I decisioned Iron Mike earlier this year.

Ninja Gaiden was also a toughie, but I had never owned or borrowed the game long enough back in the day to give it a serious shot. However, I got the game and finished it earlier this year also.

A real doozy that kicked my butt was Super Ghouls n Ghosts. Like Ninja Gaiden originally, I had only rented it, but realized that it would be a mamma jamma to beat. I got this on GBA a few years ago and still haven't beat it.

Battletoads, F-Zero GX, and quite a few shmup's are cruel in their difficulty, but I haven't put enough time in them to say I gave it a good effort.