First Minister Carwyn Jones says there is “room for optimism” despite an ominous start for the new operators of Wales and Borders rail services.
French-Spanish joint venture KeolisAmey has taken over the franchise.
The first full day has been marred by cancellations due to Storm Callum and problems with the Welsh-language online service.
However Mr Jones said: “Over the next five years people will see a real difference in quality and frequency.”
This is the first time the Welsh Government has had control over the £5bn franchise, which will be overseen by Transport for Wales (TfW), which has promised to transform the service over the next 15 years.
However the new era began with familiar problems of cancellations, delays and replacement bus services, because of flooding caused by Storm Callum.
Some passengers tweeted their frustrations about the service.
Mr Jones said: “Other countries manage it where the weather is far more unpredictable. There’s no reason why we shouldn’t.”
The change comes as the public takes more journeys by train.
Extra services will be added from December but most of the biggest promised changes will not happen for at least a couple of years.
It includes five new stations and £194m spent on cleaning every station in Wales.
Mr Jones said: “In the next five years, people will see the ramp up of services but it won’t happen overnight.
“There’s room for optimism because for 15 years there was no sign of anything changing.”
It followed the troubled tenure for Arriva Trains Wales, heavily criticised for overcrowding on commuter services.
KeolisAmey has been given targets on punctuality and overcrowding, with potential financial penalties, and profits limited to 5%.
Mr Jones said: “The difference is we control it as Welsh Government. Now we can ensure services are better over the next 15 years.
“Of course, if things go wrong, we’ll be in the firing line.
“We would have preferred to run the service ourselves but he UK government told us we couldn’t, even though the Scots can,”
KeolisAmey promises to eventually replace all trains, at a cost of £800m.
There is also £738m to electrify the South Wales valleys lines, add more services and launch the new South Wales Metro over the next 15 years.
Mr Jones said: “Half the new trains will be made in Wales, creating jobs in Wales. Secondly, the infrastructure needs to be put in place for electric services.”
Meanwhile he said he will look into why it is not possible to buy a ticket in the Welsh language because of problems with the website and app.
He said: “It’s essential there is a bilingual service.”