Depends on what consoles you're trying to capture. If you're trying to capture consoles in standard definition using composite or s-video then a gv-usb2 is the best capture card for that.
For capturing in HD using hdmi you have a bunch of options, but for the best quality you'll want to get an internal capture card (I've personally heard good things about elgato internals). It should be noted that HD capture cards are much more expensive ($40 for gv-usb2 vs $150+ for an HD capture card). External HD capture cards are cheaper but tend to have slight delay so factor that in as well.
Technically Capture Card is under the Umbrella term of Capture Devices. What you might mean is something like the Capture Card mod for 3DS vs a Capture Card like the Elgato Game Capture HD (of which there's the HD that also has composite in and the above mentioned Pro version, which is an internal PCI-E Card).
Capture Mods like for the 3DS are only a thing for Handhelds and the WiiU gamepad. There currently isn't one for the switch, as it would only be required for a very small selection of games, but there may be in the future (probably from Keity/Katsukity). For actual living room consoles (also including WiiU and Switch of course) you are going to want to follow Timmiluvs' advice above.
I personally have been using Avermedia internal capture cards and even tho they only take hdmi input you can covert older inputs to hdmi keeping the same if not improved quality depending on what ur willing to spend in general things like a framemiester or even just a rca to hdmi would work fine since I use that instead and works great for gbc, psx or ps2 etc.
Tho one thing you may need for some newer systems with hdmi inputs is a splitter that removes built in hdcp that prevents capturing consoles like the ps3 or xboxone afaik.
Elgato is another slightly less expensive route does have delays and has more options in the variety of inputs either with and internal or external capture. Best to do a bit if research on them and see what u want to go for price wise and then look at what you'll need to get working the way you want before hand.
Handheld consoles like the 3ds require capture devices installed to them and atm is costly due to only a few know sources that provide the service and it's still new hopefully there will be better alternatives down the road for that.