I've travelled a lot around Europe. In no particular order:
Deutsche Bahn [Germany] (as you hinted) is considered a national embarassment to the Germans, and its neighbours are weary of its poor punctuality. €63 for unlimited monthly travel on regional transport is a nice perk though, even if the intercity service is falling apart.
SNCF [France] is often highly rated by tourists for the performance of its TGVs. However the insistence on booking a specific train rather than just being able to turn up and go makes TGVs a poor choice compared to travel in Switzerland, or using a flexible ticket in the UK. In the regions its a bit more variable. Taking tourists between Nice and Monaco (the sort of line that OP appears to be using) is big business, so they put on a mixture of four and eight car trains (the four car ones really struggle with crowding). Regional trains out of cities like Lyon and Strasbourg however use ancient equipment, older than virtually anything used in the UK (the only real exceptions being the Inter7City sets in Scotland). Live down a rural branch line? In the UK, you probably have a few trains per day. In France there might be a morning commuter train to town and one back in the evening, no more.
NS [Netherlands] provides a pretty decent, regular service to most of the country. Contactless payments nationwide, integration between transport modes, walkable and bikeable infrastructure. Not much to complain about.
SNCB [Belgium] a reasonably decent service, if not quite as good as the Netherlands. They really need to get a grip on their graffiti problem though.
CfL [Luxemburg] has free transport nationwide. It's a perk of being a tax haven. Our trains would be swamped if we tried that. Not a bad network of trains and buses connecting what is a fairly rural country.
SBB/CFF/FFS [Switzerland] is the gold standard. Not the fastest (it's not the easiest terrain to work with), but regular interval services nationwide, connections that work, exemplary punctuality, impressive infrastructure investment, and for 3995F you can buy a GA card, giving you a year's unlimited travel on all modes of public transport.
Trenitalia [Italy] has a decent high speed network if you're going between major cities in the north. Anything south of Naples will be dreadfully slow.
CFR [Romania] uses ancient equipment, routes are very slow.
BDZ [Bulgaria] like Romania, but worse.
MAV [Hungary] good in patches.
Malta no longer has trains or trams. The buses meanwhile are dreadfully crowded and get caught in the dire congestion. Cycling infrastructure is nonexistent and the pedestrian path sometimes just narrows to nothing and you have to walk in the street. You'd think that a small island microstate would be one of the best, wouldn't you? But no...
PKP [Poland] has a reasonable network and prices are cheap. Not the most modern in many places, but still comfortable.
OBB [Austria] is somewhere between Switzerland and Germany. It's reliable, but coverage could be better, especially in rural areas.
Istanbul - I can't judge the rest of Turkish railways as the only external train was the sleeper from Sofia (comfortable, cheap, you have to get up in the small hours for customs checks). In Istanbul itself, the metro and trams are modern, but i've never seen overcrowding like it.
Elron [Estonia] very modern trains and trams around Tallinn. The service towards the Latvian border is very slow, under the USSR the lines to Moscow were the important ones. It's reasonably priced though, like €35 for a single from Tallinn to Riga. An EU project is ongoing to build a new line.
LDZ [Latvia] beginning to modernise, but still dreadfully slow
LTG [Lithuania] had quite old equipment when I visited, but I think those have been replaced since. Again, slow. When going to Poland you have to change trains because the Soviets built their track to a different gauge. Earthworks for Rail Baltica are making good progress.
IE [Ireland] do at least put on long enough trains for the demand. Frequencies are a bit lacking, especially towards the west. Outside of the DART, everything is diesel-powered and not necessarily that modern. If you want to go between any two places, you'll probably have to go via Dublin as most cross-country lines got closed.
NIR [Northern Ireland] modern, plenty of capacity. I'd like to see better frequencies though, especially towards Derry/Londonderry.
So what about the UK? We do have significant problems with crowding. On London commuter flows, that's because our economy is heavily geared towards London and it's got to the stage that we can't really add much more capacity. Put some investment into cities with room like Manchester and Leeds, and businesses will relocate and spread the load. Might do something about the insanse house prices in the South East too. Unfortunately previous governments have neglected the need to improve the connectivity of those northern cities, otherwise we'd have had HS2 years ago. And yes, we need it. Other routes like Crosscountry are easier to solve - the government could order longer trains tomorrow if it wanted to, and the infrastructure work required would be minimal. An effect of the lack of capacity on our network and the refusal to invest is that the answer to overcrowding has long been to hike fares to price people off.
On the other hand, we provide a far better service on rural routes than you'd get in most other countries. With the Pacers gone, the average age of our trains is reasonably low. Punctuality-wise, even Avanti isn't any worse than Deutsche Bahn.