Games

Run n’ guns: Contra III: Alien Wars and Pocky & Rocky

Smups: Space Megaforce

• Contra: Hard Corps(Sega Genesis) is an old side scrolling shooter, has local co-op.
• Cuphead(PC) is an old school side scrolling shooter, has local co-op.
• Enter the Gungeon(PC) is a top down roguelike shoot em up, has local co-op.
• Furi(PC) is a top down boss fighting game.
• Gauntlet reboot(PC) is the adaptation of an old franchise, has 4p local co-op.
• Geometry wars(PC) is a shoot em up series.
• Mega Man Zero(GBA) is a side scrolling platformer series.
• Risk of Rain(PC) is a roguelike shoot em up series, has local co-op.
• Touhou Project(PC) has a bunch of games like Gunbird in the series.
• Vampire Survivors(PC) is a top down shoot em up, has local co-op.

Shmups, I'm only a beginner but I have a few suggestions:

• ESP Ra.De. - somewhat slower bullet hell with pretty interesting scoring, the "Psi" re-release has a lot of useful QoL features.
• Espgaluda II - you could think of it as a successor to the former, it has refined gameplay and recent releases have great QoL features. Somewhat faster paced bullet hell?
• Ikaruga / Radiant Silvergun - Although these are two very different games, they have entirely different mechanisms to most other shmups. Ikaruga feels like a "puzzle" game a lot of the time, while Radiant Silvergun has some light RPG elements. Both are somewhat hard to get into imo.
• Dodonpachi Resurrection - great starting point re bullet hells, the recent re-release offers a ton of QoL features and the game itself has interesting scoring / gameplay. Soundtrack is awesome.
• Raiden IV - Super biased, but I love the soundstrack. Pretty great, if simple, game otherwise.

I have many more shmups in my backlog (Ketsui, Dodonpachi Daioujou, Battle Garegga, Rolling Gunner, etc) which I'm sure I could recommend, but seeing as I haven't played them first hand yet... I'll leave it there for now.

Without a shadow of a doubt, Metal Slug

I like Xevious and Zaxxon. Zaxxon was cool because it had a unique isometric perspective that I haven't seen in another game.

Gradius 3 specifically I found to be quite fun. Its too bad Konami retired the Gradius series, but I suppose its probably better that way.

The Panzer Dragoon series is a great arcade shooter series.

Contra. Contra 4 specifically on the Nintendo DS I felt had the perfect balance. I really liked that entry.

Shmup: R-Type Delta, but you really can’t go wrong with any of them.

Run ‘n Gun: Gunstar Heroes, love the weapon power up system and its co-op.

How about autoscrolling shmups where you don't die after every hit and get to upgrade your ship between missions?

The oldschool entry in this niche would be Tyrian – released in 1995, made freeware in 2004, then ported to modern OSes.

2004 was also when Jets'N'Guns came out. It looks more modern, has a quirky sense of humor and a badass metal soundtrack. It also has a sequel.

Both games can be found on your (PC) digital marketplace of choice.

Some more modern run and guns - Blazing Chrome and Huntdown. Both of those are a good time.

I played the fuck out of Cannon Spike on Dreamcast

https://en.wikipedia.org/wiki/Cannon_Spike

But I was a huge SmashTV fan back in teh day. I still play it when I see a cabinet.

I tried to get into the mindset to get good at Ikaruga but I just cannot invest that kinda time.

Dreamcast had so many good shmups.

Guardian Legends and 1942.

I really like Gunlocked, which is a more short-form and arcadey roguelite shmup

Sunset Riders is a great run and gun.